Practice Inverse Variation in Math

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

A relationship where y=kx: as one quantity doubles, the other halves—their product stays constant.

More workers means less time: if 4 workers take 6 hours, 8 workers take 3 hours.

Showing a random 20 of 50 problems.

Example 1

medium
A loud speaker's perceived loudness varies inversely with the square of distance. If it is 80 at 3 m, find loudness at 6 m.

Example 2

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y=kx. If x is multiplied by 5, by what factor does y change?

Example 3

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y varies inversely with x, and y=8 when x=3. Find k and the equation. Then find y when x=6.

Example 4

easy
Can x=0 in the inverse variation y=kx?

Example 5

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A test pilot finds time-to-cover 1 km varies inversely with average speed. At 40 km/h it takes 90 s. Find time at 60 km/h.

Example 6

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If y varies inversely with x2 and y=4 when x=3, find y when x=6.

Example 7

easy
y varies inversely with x, and y=3 when x=8. Find y when x=12.

Example 8

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y varies inversely with x. Given two pairs (2,12) and (a,4), find a.

Example 9

easy
Does the equation xy=−12 describe an inverse variation?

Example 10

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y=kx passes through (2,18) and (a,4). Find a.

Example 11

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The pressure P and volume V of a gas at constant temperature satisfy PV=k. If P=4 atm when V=6 L, find P when V=8 L.

Example 12

challenge
y varies inversely with x. When x increases by 50%, y decreases by how many percent?

Example 13

easy
In y=k/x, if x triples, what happens to y?

Example 14

challenge
y varies inversely with x. If y values at x=2 and x=5 differ by 9, find k.

Example 15

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Quantities satisfy xy=k. If x and y are positive integers and k=24, how many ordered pairs (x,y) exist?

Example 16

easy
If y varies inversely with x and y=9 when x=4, find k.

Example 17

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It takes 6 pipes 8 hours to fill a tank. How many pipes fill it in 4 hours?

Example 18

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y varies inversely with x2. When x=2, y=18. Find y when x=6.

Example 19

easy
In y=kx, what happens to y when x doubles?

Example 20

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A trip takes 4 hours at 60 mph. How fast must you drive to make it in 3 hours?