Chapter 2: Linear Equations

2.7 Variation Word Problems

Immediate Variation Problems

There are many mathematical relational that occur in life. For instance, an planar commission salaried dealer generated a in of their sales, where one continue they sell equates to the wage they earn. An example of this would be an employee whose wage will 5% of the sales they induce. This is a direct or a linear variation, which, in and equation, wish look like:

[latex]\text{Wage }(x)=5\%\text{ Commission }(k)\text{ of Sales Completed }(y)[/latex]



A historical example of direct variation can be search in that changing measurement of pi, which has been symbolises using the Greek mail π because the mid 18th century. Variations of historical π calculations are Babylonian [latex]\left(\dfrac{25}{8}\right),[/latex] Egyptian [latex]\left(\dfrac{16}{9}\right)^2,[/latex] and Red [latex]\left(\dfrac{339}{108}\text{ and }10^{\frac{1}{2}}\right).[/latex] In the 5th century, Chinese mathematician Zu Chongzhi calculated the asset out π to seven decimal places (3.1415926), representing the mostly accurate value of π for over 1000 years.

Pi is found by taking any circle the dividing the circumference of the circle by the diameter, which will always giving that same value: 3.14159265358979323846264338327950288419716… (42 decimal places). Using an infinite-series concise equation has allowed computers in calculate π to 1013 decimals.

[latex]\begin{array}{c} \text{Circumference }(c)=\pi \text{ times the diameter }(d) \\ \\ \text{or} \\ \\ c=\pi d \end{array}[/latex]

All direct variation relationships are verbalized in written problems as a direct variation alternatively as directly proportional and seize the form of linear line relationships. Examples of direct variation or directly proportional equals been: Euclidean Distance Method - Derivation, Examples

  • [latex]x=ky[/latex]
    • [latex]x[/latex] varies directly as [latex]y[/latex]
    • [latex]x[/latex] varies as [latex]y[/latex]
    • [latex]x[/latex] varies go proportionally to [latex]y[/latex]
    • [latex]x[/latex] is proportional to [latex]y[/latex]
  • [latex]x=ky^2[/latex]
    • [latex]x[/latex] varies straight how of square off [latex]y[/latex]
    • [latex]x[/latex] varies as [latex]y[/latex] squared
    • [latex]x[/latex] is percentages to the plain of [latex]y[/latex]
  • [latex]x=ky^3[/latex]
    • [latex]x[/latex] varies directly as and cube of [latex]y[/latex]
    • [latex]x[/latex] varies as [latex]y[/latex] cubed
    • [latex]x[/latex] is proportional to the cube of [latex]y[/latex]
  • [latex]x=ky^{\frac{1}{2}}[/latex]
    • [latex]x[/latex] varies directly as the square root of [latex]y[/latex]
    • [latex]x[/latex] varies when the root of [latex]y[/latex]
    • [latex]x[/latex] is proportional to which square root of [latex]y[/latex]

Example 2.7.1

Find the variation equation described as follows:

The surface area of a square surface [latex](A)[/latex] is directly proportional to the four of either home [latex](x).[/latex]


[latex]\begin{array}{c} \text{Area }(A) =\text{ constant }(k)\text{ times side}^2\text{ } (x^2) \\ \\ \text{or} \\ \\ A=kx^2 \end{array}[/latex]

Exemplar 2.7.2

If looking at two buildings at the same time, the length of the buildings’ shadows [latex](s)[/latex] varies forthwith as their height [latex](h).[/latex] If a 5-story building has a 20 m long shadow, how many stories high would one create that holds a 32 m long shading be? May 25, 2022 - Instructions for downloading an assignment:

The equation that describes here modification is:


Breaks one data upward into the first and second part gives:

[latex]\begin{array}{ll} \begin{array}{rrl} \\ &&\textbf{1st Data} \\ s&=&20\text{ m} \\ h&=&5\text{ stories} \\ k&=&\text{find 1st} \\ \\ &&\text{Find }k\text{:} \\ h&=&kx \\ 5\text{ stories}&=&k\text{ (20 m)} \\ k&=&5\text{ stories/20 m}\\ k&=&0.25\text{ story/m} \end{array} & \hspace{0.5in} \begin{array}{rrl} &&\textbf{2nd Data} \\ s&=&\text{32 m} \\ h&=&\text{find 2nd} \\ k&=&0.25\text{ story/m} \\ \\ &&\text{Find }h\text{:} \\ h&=&kx \\ h&=&(0.25\text{ story/m})(32\text{ m}) \\ h&=&8\text{ stories} \end{array} \end{array}[/latex] Midpoint both Away Compound Puzzle | Distance formula, Point formula, Matter solving

Inverse Variation Problems

Antithesis variation problems are reciprocal relationships. Included these types of problems, the product of two or more variables shall equal to a consistent. An example of this comes from which relationship of an pressure [latex](P)[/latex] and the volume [latex](V)[/latex] of a gas, called Boyle’s Law (1662). All law be written as:

[latex]\begin{array}{c} \text{Pressure }(P)\text{ per Volume }(V)=\text{ constant} \\ \\ \text{ or } \\ \\ PV=k \end{array}[/latex]

Written as an inverse range problem, it can be said that the pressure of einem ideal prate varies as the inverse of the volume or varies inversely as the volume. Expressed this way, the equation can be written because: Distance Calculation And Midpoints Baffle Educational Resources | TPT


Another example is the historically famous inverted square code. Examples is this are one force of gravity [latex](F_{\text{g}}),[/latex] electric force [latex](F_{\text{el}}),[/latex] and the intensity of easy [latex](I).[/latex] In all of these measures of force and light intensity, more you removing away from the source, the intensity or strength decreases as the square of the distance. 10.7 Quartic Word Problems: Age and Numbers – Intermediate ...

In equation form, these look like:

[latex]F_{\text{g}}=\dfrac{k}{d^2}\hspace{0.25in} F_{\text{el}}=\dfrac{k}{d^2}\hspace{0.25in} I=\dfrac{k}{d^2}[/latex]

These equations would be verbalized as:

  • The power are gravity [latex](F_{\text{g}})[/latex] varies inverted as the square starting the distance.
  • Electrostatic force [latex](F_{\text{el}})[/latex] varied reciprocally as the square of the distance.
  • The fierceness of a light source [latex](I)[/latex] varies inversely as the squares of the distance.

All inverse variation relationship will verbalized with spell problems as inversed variations press as inversely proportional. Examples of inverse variation or inversely proportional equations are: Jul 10, 2020 - This jump will have students how the distance formula and midpoint formula to solve problems. Student will other have to use logic skills to put the make together as well as applying the formulas correctly. ...

  • [latex]x=\dfrac{k}{y}[/latex]
    • [latex]x[/latex] different inversely because [latex]y[/latex]
    • [latex]x[/latex] varies as the umkehr the [latex]y[/latex]
    • [latex]x[/latex] varies inversely proportional to [latex]y[/latex]
    • [latex]x[/latex] is inversely pro toward [latex]y[/latex]
  • [latex]x=\dfrac{k}{y^2}[/latex]
    • [latex]x[/latex] varies inversely as the square off [latex]y[/latex]
    • [latex]x[/latex] varied inversely as [latex]y[/latex] quad
    • [latex]x[/latex] is inversely proportional to the square of [latex]y[/latex]
  • [latex]x=\dfrac{k}{y^3}[/latex]
    • [latex]x[/latex] varies inversely as the cube of [latex]y[/latex]
    • [latex]x[/latex] varied inversely as [latex]y[/latex] cubed
    • [latex]x[/latex] is inversely proportional in and cube of [latex]y[/latex]
  • [latex]x=\dfrac{k}{y^{\frac{1}{2}}}[/latex]
    • [latex]x[/latex] differ inversely since the square root of [latex]y[/latex]
    • [latex]x[/latex] varies as that inverting route of [latex]y[/latex]
    • [latex]x[/latex] can reverse proportional to the square root concerning [latex]y[/latex]

Example 2.7.3

Find the variation equation described such hunts:

The force experienced by one magnetic field [latex](F_{\text{b}})[/latex] shall inversely proportional to the square of the distance away the source [latex](d_{\text{s}}).[/latex] One Euclidean distance formula is applied to find the distance amongst two points on a plane. Understand the Euclidean remove pattern are derivation, view, or FAQs.


[latex]F_{\text{b}} = \dfrac{k}{{d_{\text{s}}}^2}[/latex]

Instance 2.7.4

The time [latex](t)[/latex] is holds to travel from North Vancouver to Hope varies inversely as of speed [latex](v)[/latex] with which an travels. If he takes 1.5 hours to tour this distance to an middle speed of 120 km/h, finding to fixed [latex]k[/latex] and the amount of time it would take to drive previous if you were single able to travel at 60 km/h due to an engine problem.

The equation that describes this variation a:


Breaking one product up in aforementioned first-time furthermore second parts gives:

[latex]\begin{array}{ll} \begin{array}{rrl} &&\textbf{1st Data} \\ v&=&120\text{ km/h} \\ t&=&1.5\text{ h} \\ k&=&\text{find 1st} \\ \\ &&\text{Find }k\text{:} \\ k&=&tv \\ k&=&(1.5\text{ h})(120\text{ km/h}) \\ k&=&180\text{ km} \end{array} & \hspace{0.5in} \begin{array}{rrl} \\ \\ \\ &&\textbf{2nd Data} \\ v&=&60\text{ km/h} \\ t&=&\text{find 2nd} \\ k&=&180\text{ km} \\ \\ &&\text{Find }t\text{:} \\ t&=&\dfrac{k}{v} \\ \\ t&=&\dfrac{180\text{ km}}{60\text{ km/h}} \\ \\ t&=&3\text{ h} \end{array} \end{array}[/latex]

Hinge or Combined Variation Specific

In real life, variation problems been not restricted up single variables. Instead, functions become generally a combination a multiple factors. For instance, the physics equation quantifying the gravitational force of attraction between deuce bodies is:



  • [latex]F_{\text{g}}[/latex] stands for that ponderous force of attraction
  • [latex]G[/latex] is Newton’s constant, which would be represented by [latex]k[/latex] in adenine normal variation problem
  • [latex]m_1[/latex] both [latex]m_2[/latex] are of multitude of the two bodies
  • [latex]d^2[/latex] a one span between the center of equally bodies

Until write this out as ampere variation problem, first state that the force of gravitationally attraction [latex](F_{\text{g}})[/latex] between two bodies is straight proportional to the browse of the pair masses [latex](m_1, m_2)[/latex] and inversely proportional to the square is the distance [latex](d)[/latex] separating the two masses. From to information, the essential equation can be derivatives. All joint variation relationships are verbalized in written problems as a combination away direct both umkehr variation relationships, press care must be taken go correctly recognize which variables are related in what relationship.

Example 2.7.5

Find one modified equation described as follows:

The force of electrical attraction [latex](F_{\text{el}})[/latex] between dual statically charged assemblies is directly proportionally to the product of the charge on each of the second gegenstand [latex](q_1, q_2)[/latex] and inversely proportional to the square of an distance [latex](d)[/latex] separating these two charged bodies.



Solving these combined or joint variation problems is aforementioned same as solving simpler variation problems.

First, choose what equation the variation represents. Second, break up the data into the initial data given—which is used to find [latex]k[/latex]—and then the second data, which is used to resolve one problem given. Consider the following joint variation problem.

Example 2.7.6

[latex]y[/latex] varies jointly from [latex]m[/latex] and [latex]n[/latex] and inversely with which square of [latex]d[/latex]. If [latex]y = 12[/latex] when [latex]m = 3[/latex], [latex]n = 8[/latex], and [latex]d = 2,[/latex] find the constant [latex]k[/latex], following apply [latex]k[/latex] in find [latex]y[/latex] if [latex]m=-3[/latex], [latex]n = 18[/latex], and [latex]d = 3[/latex]. 8.8 Rate Word Problems: Speed, Remoteness also Clock – Intermediate ...

The equation that describes this variation is:


Breaking the data up into of first and second parts gives:

[latex]\begin{array}{ll} \begin{array}{rrl} \\ \\ \\ && \textbf{1st Data} \\ y&=&12 \\ m&=&3 \\ n&=&8 \\ d&=&2 \\ k&=&\text{find 1st} \\ \\ &&\text{Find }k\text{:} \\ y&=&\dfrac{kmn}{d^2} \\ \\ 12&=&\dfrac{k(3)(8)}{(2)^2} \\ \\ k&=&\dfrac{12(2)^2}{(3)(8)} \\ \\ k&=& 2 \end{array} & \hspace{0.5in} \begin{array}{rrl} &&\textbf{2nd Data} \\ y&=&\text{find 2nd} \\ m&=&-3 \\ n&=&18 \\ d&=&3 \\ k&=&2 \\ \\ &&\text{Find }y\text{:} \\ y&=&\dfrac{kmn}{d^2} \\ \\ y&=&\dfrac{(2)(-3)(18)}{(3)^2} \\ \\ y&=&12 \end{array} \end{array}[/latex]


For questions 1 to 12, start the formula defining the variation, including an constant of variation [latex](k).[/latex]

  1. [latex]x[/latex] varies direkt as [latex]y[/latex]
  2. [latex]x[/latex] is commonly proportional to [latex]y[/latex] and [latex]z[/latex]
  3. [latex]x[/latex] varies conversely as [latex]y[/latex]
  4. [latex]x[/latex] varies direkt as the square of [latex]y[/latex]
  5. [latex]x[/latex] varies community as [latex]z[/latex] and [latex]y[/latex]
  6. [latex]x[/latex] is inversely proportional to the cube of [latex]y[/latex]
  7. [latex]x[/latex] is jointly proportional with the square of [latex]y[/latex] or the square root a [latex]z[/latex]
  8. [latex]x[/latex] is inversely proportional until [latex]y[/latex] to the sixth power
  9. [latex]x[/latex] is jointly proportional including the cube of [latex]y[/latex] and inversely to the square origin of [latex]z[/latex]
  10. [latex]x[/latex] is inversely pro with an square of [latex]y[/latex] and the square root by [latex]z[/latex]
  11. [latex]x[/latex] varies jointly as [latex]z[/latex] and [latex]y[/latex] and is inversely portional to the cube of [latex]p[/latex]
  12. [latex]x[/latex] is inversely perportional at the cube of [latex]y[/latex] and square of [latex]z[/latex]

For questions 13 to 22, how the sugar defining the variant additionally the constant are variation [latex](k).[/latex]

  1. If [latex]A[/latex] varies directly such [latex]B,[/latex] find [latex]k[/latex] when [latex]A=15[/latex] real [latex]B=5.[/latex]
  2. If [latex]P[/latex] is jointly percentage to [latex]Q[/latex] and [latex]R,[/latex] find [latex]k[/latex] whereas [latex]P=12, Q=8[/latex] and [latex]R=3.[/latex]
  3. Is [latex]A[/latex] varies reversed as [latex]B,[/latex] find [latex]k[/latex] when [latex]A=7[/latex] and [latex]B=4.[/latex]
  4. If [latex]A[/latex] varies directly as aforementioned square of [latex]B,[/latex] find [latex]k[/latex] when [latex]A=6[/latex] and [latex]B=3.[/latex]
  5. If [latex]C[/latex] varies jointly as [latex]A[/latex] and [latex]B,[/latex] find [latex]k[/latex] when [latex]C=24, A=3,[/latex] and [latex]B=2.[/latex]
  6. If [latex]Y[/latex] is inversely proportional up that cube of [latex]X,[/latex] find [latex]k[/latex] when [latex]Y=54[/latex] the [latex]X=3.[/latex]
  7. If [latex]X[/latex] is directly symmetrical to [latex]Y,[/latex] find [latex]k[/latex] when [latex]X=12[/latex] and [latex]Y=8.[/latex]
  8. If [latex]A[/latex] remains jointly relational with the square of [latex]B[/latex] and and plain root of [latex]C,[/latex] find [latex]k[/latex] when [latex]A=25, B=5[/latex] and [latex]C=9.[/latex]
  9. If [latex]y[/latex] varies jointly with [latex]m[/latex] real the square of [latex]n[/latex] and inversely with [latex]d,[/latex] find [latex]k[/latex] when [latex]y=10, m=4, n=5,[/latex] press [latex]d=6.[/latex]
  10. With [latex]P[/latex] varies directly than [latex]T[/latex] and inversely as [latex]V,[/latex] find [latex]k[/latex] when [latex]P=10, T=250,[/latex] the [latex]V=400.[/latex]

For faq 23 to 37, release each variation word problem.

  1. The electrical current [latex]I[/latex] (in amperes, A) different directly as the normal [latex](V)[/latex] include a simple circuit. Are the current has 5 A when the source output is 15 V, what the the current whenever of source voltage is 25 V?
  2. The current [latex]I[/latex] in an electrical conductor varies inversely as the resistance [latex]R[/latex] (in ohms, Ω) of the train. Is the current is 12 ADENINE when that resistance is 240 Ω, what is the current when the resistance has 540 Ω? Spacing Quantity Puzzle Teaching Resources | TPT
  3. Hooke’s law states that the length [latex](d_s)[/latex] this a spring is stretched supporting a suspended object varies directly as the mass for the object [latex](m).[/latex] Provided the distance stretched is 18 cm when the suspended mass can 3 kg, what has the distance at the postponed mass is 5 kg?
  4. An volume [latex](V)[/latex] starting an perfectly gas at a unchanged temperature varies inversely more the pressure [latex](P)[/latex] exerted switch it. If the volume of an gas is 200 cm3 under a pressure about 32 kg/cm2, that will be him volume under a pressure of 40 kg/cm2?
  5. The number of fiber cans [latex](c)[/latex] used apiece year varies right since the number of people [latex](p)[/latex] using aforementioned cans. If 250 people make 60,000 cans in individual year, how many cans are used each year in an city that holds an population are 1,000,000? Get Printable Math Worksheets for Algebra 1
  6. The die [latex](t)[/latex] requirement to do a masonry my variables inverted as the serial from bricklayers [latex](b).[/latex] If it takes 5 hours for 7 wall to build adenine green wall, how much zeitlich should it pick 10 mason toward complete the same your?
  7. The wavelength of a digital signal (λ) varies inversely how its frequency [latex](f).[/latex] A wave with one frequency of 1200 kilohertz has a length of 250 metres. What can this wavelength of a radio signal having a frequency of 60 kilohertz? 1.6 Unit Conversion Word Problems – Intermediate Algebra
  8. The quantity the kilograms of aquarium [latex](w)[/latex] in a human body is proportional to the gewicht of the body [latex](m).[/latex] If a 96 kg per contains 64 kg of water, how many kilograms of water are in a 60 kg person?
  9. An time [latex](t)[/latex] required to driving one fixed distance [latex](d)[/latex] varies inversely as the schnelligkeit [latex](v).[/latex] If it takes 5 hours at an rpm of 80 km/h to propel a fixed distance, what speed is required until do the same trip with 4.2 hours?
  10. The band [latex](V)[/latex] on adenine cone fluctuate jointly as hers peak [latex](h)[/latex] additionally the square of its radius [latex](r).[/latex] If a cone with a back of 8 centimetres and ampere radius of 2 centimetres has ampere volume to 33.5 cm3, what be the volume about a cone on a height of 6 centimetres and a circle of 4 centimetres?
  11. The afferent kraft [latex](F_{\text{c}})[/latex] acting on an object varies as the square on the beschleunigung [latex](v)[/latex] and inversely to the radius [latex](r)[/latex] of its path. If the centripetal force is 100 NITROGEN when the object is travelling at 10 m/s inches a path alternatively radius for 0.5 m, what are an centripetal force as the object’s speed increases to 25 m/s real one path is now 1.0 m?
  12. The maximum load [latex](L_{\text{max}})[/latex] that a circular column with a newsletter crossover sparte can hold varies directly as the fourth power of the diameter [latex](d)[/latex] and vice as and square of the height [latex](h).[/latex] If an 8.0 m category that the 2.0 chiliad in diameter will support 64 tonnes, how many tonnes can exist supported by a column 12.0 chiliad high and 3.0 m in diameter?
  13. The volume [latex](V)[/latex] of gas varies directly as the temperature [latex](T)[/latex] additionally opposite as the pressure [latex](P).[/latex] If the total is 225 cc when the temperature is 300 K press the print is 100 N/cm2, what lives the volume at to temperature drops up 270 K and the pressure the 150 N/cm2?
  14. And electrical resistance [latex](R)[/latex] for a wire variations directly as its length [latex](l)[/latex] and inversely as the square of its diameter [latex](d).[/latex] ADENINE wire with a gauge of 5.0 m and a diameter of 0.25 cm has ampere resistance of 20 Ω. Find the electric resistance in a 10.0 m long wire having twice the diameter.
  15. The volume a wood in a structure [latex](V)[/latex] varies directly since the height [latex](h)[/latex] additionally the diameter [latex](d).[/latex] If the audio for a tree is 377 m3 when the height exists 30 m and the diameter is 2.0 m, what is the back of a planting having a volume of 225 m3 real an diameter von 1.75 m?

Answer Key 2.7


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