act-dog

A. Incorrect. Use the fact that there are 5,280 feet in 1 mile, 60 minutes in 1 hour, and 60 seconds in 1 minute to set up a unit conversion problem. Be careful to multiply so that the units cancel to leave feet per second as the final unit. You may have multiplied incorrectly and then chosen the closest answer

B. Incorrect. You may have thought the speed in feet per second would be the same as the speed in miles per hour. Instead, use the fact that there are 5,280 feet in 1 mile, 60 minutes in 1 hour, and 60 seconds in 1 minute to set up a unit conversion problem. Be careful to multiply so that the units cancel to leave feet per second as the final unit.

C. Correct. Use the fact that there are 5,280 feet in 1 mile, 60 minutes in 1 hour, and 60 seconds in 1 minute to set up a unit conversion problem. Be careful to multiply so that the units cancel to leave feet per second as the final unit: $\frac{30 \text{miles}}{1 \text{hour}}\times \frac{1 \text{hour}}{60 \text{minutes}}\times \frac{1 \text{minute}}{60 \text{seconds}}\times \frac{5,280 \text{feet}}{1 \text{mile}}=\frac{30\left(5,280\right) \text{feet}}{60\left(60\right) \text{seconds}}=44 \frac{\text{feet}}{\text{second}}$.

D. Incorrect. You may have divided the numbers given in the problem, $\frac{5,280}{30}=176$. Instead, use the fact that there are 5,280 feet in 1 mile, 60 minutes in 1 hour, and 60 seconds in 1 minute to set up a unit conversion problem. Be careful to multiply so that the units cancel to leave feet per second as the final unit.