Question

The value of y varies directly with x, and y = 18 when x = 12. Find y when x = 60.

Answer 1

Since the value of y varies directly with x, the ratio of y to x is always constant. We can set up the proportion:

y/x = 18/12

Then we can solve for y by cross multiplying:

y = (18/12)x

= (3/2)x

= (3/2)(60)

= 90

So when x = 60, y = 90.