Given: y varies directly as x.
If y = 5 when x = 4, what is the value of y when x = 12?
Since y varies directly as x, we can set up the equation y = kx, where k is the constant of proportionality.
To find k, we can use the initial values given:
5 = k * 4
k = 5/4
k = 1.25
Now that we have found the value of k, we can use it to find y when x = 12:
y = 1.25 * 12
y = 15
Therefore, when x = 12, y = 15.