Final answer:
The value of y, which varies directly with x, is 360 when x = 2.25, calculated using the constant of proportionality found from given values of y = 80 when x = 1/2.
Step-by-step explanation:
The value of y varies directly with x. This means that when x increases, y also increases by a proportionate amount and vice versa. To find the constant of proportionality, we use the given values of y = 80 when x = 1/2. The constant of proportionality (k) is calculated by dividing y by x:
k = y / x = 80 / (1/2) = 160
Now, to find the value of y when x = 2.25, we use the constant of proportionality:
y = k * x = 160 * 2.25 = 360
Therefore, the value of y when x = 2.25 is 360.