GMAT Practice Question: A certain bridge is 4,024 feet long. Approximately how many minutes does it take to cross this...
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)
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Topics: word problems, conversions, rates, translations, approximations
Solution
Step 1
We apply the distance formula which states that the distance traveled equals the speed multiplied by the time.
\text{Distance} = \text{Speed} \times \text{Time}
Step 2
We convert \textbf{\text{"20 miles per hour"}} into feet per minute using the conversion factor \textbf{\text{"1 mile = 5280 feet"}} and there are 60 minutes in an hour.
20 \times 5280 \div 60 = 1760 \text{ feet/minute}
Step 3
We solve for the time in minutes by dividing the bridge length by the speed in feet per minute.
t = \frac{4024}{1760}
Step 4
We simplify the fraction by canceling the common factor 8.
\frac{4024}{1760} = \frac{\cancel{8} \times 503}{\cancel{8} \times 220} = \frac{503}{220}
Step 5
We approximate the quotient to find the time in minutes.
\frac{503}{220} \approx 2.29 \text{ minutes}
Answer
Approximately 2 minutes, so option B.
