Question

If x and y are in direct proportion and y is 54 when x is 9, find y when x is 15.

Answer 1

x and y are directly proportional, which means:

x = ky

Now, substitute the given values to find the constant (k):

x = ky

9 = k(54)

9/54 = k

1/6 = k

k = 0.17 (2 d.p.)

Our equation is x = 0.17y

Now, substitute x = 15 to get the value of y:

x = 0.17y

15 = 0.17y

15/0.17 = y

y = 88.24 (2 d.p.)

Hope this helps!!