Question

A certain bridge is 4,024 feet long. Approximately how many minutes does it take to cross this bridge at a constant speed of 20 miles per hour? (1 mile = 5,280 feet)

• A. 1.7
• B. 2.3
• C. 4.2
• D. 6.1

Answer 1

The Correct Option is B

Convert the speed from miles per hour to feet per minute:
\[ 20 \text{ miles per hour} = 20 \times 5280 \text{ feet per hour} = 105600 \text{ feet per hour} \]
\[ \text{Feet per minute} = \frac{105600}{60} = 1760 \text{ feet per minute} \]

The time to cross the bridge is the length of the bridge divided by the speed:
\[ \text{Time} = \frac{4024}{1760} \approx 2.3 \text{ minutes} \]

To convert speed from miles per hour to feet per minute, multiply by 5280 and divide by 60. Then divide the distance by the speed to find the time.