If y varies directly as the cube of x, what is the value of y in the ordered pairs (4,16) and (2,y)?

1 Answer
Jul 3, 2016

y=2

Explanation:

We can interpret "y varies directly as the cube of x" as following formula:

y=kx^3, where k = some constant that we need to find.

We are given one order pair (4,16) from which we can find the value of k.

So, 16=k*4^3

16=k*64

k=16/64 = 1/4

Now, we can use our original formula y=kx^3 and pluging 1/4 for k. That would give us y=1/4x^3.

To find y in (2,y), we just need to plugin 2 for x.

y=1/4*2^3

y=1/4*8

y=2