Question

If x varies directly with y and x = 6 when y = 15, find x when y= 20.

Answer 1

8

Explanation:

Varies directly think y=kx

Varies indirectly think y=k/x

We have first option so y=kx

x=6 and y=15 means we have 15=k(6)

So k=15/6 or reducing gives=5/2

So we just found our constant of proportionality, this number never changes. It stays the same no matter what x or y they give you...

So the equation is y=5/2 *x

Now what is x if y=20

Plug in 20=5/2 *x

So x=20*2/5=40/5=8