Question

Y is inversely proportional to the cube of x if y = 7 when x=4 what is y when x is 5

Answer 1

y = 3.584

Explanation:

Given

Variation = Inverse Proportional

When y = 7, x = 4

Required

Find y when x = 5

First, we need to represent the variation.

y varies inversely proportional to x³

This implies that

y ~ 1/x³

Convert variation to equation

y = k/x³

Make k the subject

k = x³y

When y = 7, x = 4

This gives:

k = 4³ * 7

k = 64 * 7

k = 448

To determine the value of y when x = 5;

We make use of y = k/x³

Substitute 5 for x and 448 for k

y = 448/5³

y = 448/125

y = 3.584