Question

Y is inversely proportional to a^3 when a = 2, y = 10.

A is directly proportional to x, when x = 4 a = 20.

Find a formula for y in terms of x. Give your answer in its simplest form.

Answer 1

Answer:

Y is inversely proportional toa^3

so, Y=k/a^3 where k is constant

when a=2,y=10

then , 10=k/2^3

=> k=10×2^3=10×8=80

Y=80/a^3

again,

Ais directly proportional to x

so , A= k.x

when x=4,a=20

then, 20=k.4

=> k=20/4=5

so, a=5x

putting the value of a

Y=80/a^3

Y=80 /(5x)^3

Y= 80/125x^3

Y=16/25x^3