Question

If y varies directly as x^2 and y=400 when x=16,find y when x=4.

Answer 1

25

Explanation:

If y varies directly as x^2, we can write:

y = kx^2

where k is the constant of proportionality.

To find k, we can use the given information that y = 400 when x = 16:

400 = k(16)^2

400 = 256k

k = 400/256

k = 1.5625

Now that we know the value of k, we can use the equation y = kx^2 to find y when x = 4:

y = 1.5625(4)^2

y = 25

Therefore, when x = 4, y is 25.