Question

If y varies directly as x, and y = 36 as x = 9, find y for the x-value 5.

Answer 1

If y varies directly as x, then:
y = kx, for some constant k.

Since y = 36 when x = 9, we see that:
36 = 9k ==> k = 4.

So, the equation that relates x and y is:
y = 4x.

Therefore, when x = 5:
y = 4(5) = 20

Answer 2

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