ACT Math · Ratios, rates, and percents
A cyclist rides 60 miles at 30 miles per hour, then rides another 90 miles at 45 miles per hour. What is the cyclist's average speed for…
A cyclist rides 60 miles at 30 miles per hour, then rides another 90 miles at 45 miles per hour. What is the cyclist's average speed for the entire trip?
Answer and explanation
Answer: G: 37.5 mph
Average speed is total distance divided by total time, not a simple average of the two speeds. Time for the first leg: 60/30=2 hours. Time for the second leg: 90/45=2 hours. Average speed = (60+90)/(2+2) = 150/4 = 37.5 mph. Choice J reports the simple numeric average of the two distances divided by an incorrect combined rate assumption, landing on a higher value than the correctly time-weighted result.
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