Question

If y varies directly as x, and y is 18 when x is 5, which expression can be used to find the value of y when x is 11

Answer 1

expression: y = 3.6x

for x = 11, then y = 39.6

Explanation:

Direct variation uses the following equation:

y = kx

For each case, there will be an actual number instead of k.

We need to find which value of k our problem uses. We can use teh given x and y values, and solve for k.

y = kx, use x = 5 and y = 18, and solve for k

18 = k * 5

k = 18/5 = 3.6

In our case, k = 3.6, so the specific equation for direct varuiation for this problem is

y = 3.6x

Now we can find y when x = 11.

y = 3.6x

y = 3.6(11)

y = 39.6