A train travels at a constant speed of 54 kilometers per... | SAT Ratios, rates, proportional relationships, and units Question, Answer Explained

Question bank / Ratios, rates, proportional relationships, and units

Math · Problem-Solving and Data AnalysisMedium

A train travels at a constant speed of $54$ kilometers per hour. What is this speed in meters per second? ( $1$ kilometer $= 1{,}000$ meters)

$0.9$

$15$

$194.4$

$900$

Show answer and explanation

Answer: B

In one hour the train travels $54 \times 1{,}000 = 54{,}000$ meters. One hour is $60 \times 60 = 3{,}600$ seconds. So the speed is $\frac{54{,}000}{3{,}600} = 15$ meters per second.

Choice D divides by $60$ only once, which gives the speed in meters per minute.

Why the other choices are wrong

A. This divides 54 by 60, which skips the conversion from kilometers to meters and from minutes to seconds.
C. This multiplies 54 by 3.6. To go from kilometers per hour to meters per second, divide by 3.6.
D. 900 is the speed in meters per minute. Divide by 60 again to get meters per second.

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