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12 May 2021, 06:15
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D
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Difficulty:
15%
(low)
Question Stats:
82% (01:27) correct
18%
(01:51)
wrong
based on 93
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Barbara walked up and down a 25 meter long corridor. When she walked one way, she walked at 4 meters per second, and when she walked the other way, her speed was 2 meters per second. What was her average speed in meters per second?
A. \(1 \frac{1}{3}\)
B. \(1 \frac{2}{3}\)
C. \(2 \frac{1}{3}\)
D. \(2 \frac{2}{3}\)
E. 3
A. \(1 \frac{1}{3}\)
B. \(1 \frac{2}{3}\)
C. \(2 \frac{1}{3}\)
D. \(2 \frac{2}{3}\)
E. 3
12 May 2021, 07:16
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Time = Distance/Speed
Time of first trip: 25/4
Time of second trip: 25/2
Total time: 25/4 + 25/2
= 25/4 + 50/4
= 75/4
Total distance: 50
Average speed = total distance/total time
50/(75/4)
= 50*(4/75)
= 200/75
= 2 50/75
= 2 2/3
Answer D
Time of first trip: 25/4
Time of second trip: 25/2
Total time: 25/4 + 25/2
= 25/4 + 50/4
= 75/4
Total distance: 50
Average speed = total distance/total time
50/(75/4)
= 50*(4/75)
= 200/75
= 2 50/75
= 2 2/3
Answer D
13 May 2021, 22:54
Kudos
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To calculate the avg speed for round trips, use the below formula:
avg.speed = 2ab/(a+b), where a and b are the respective speeds.
Avg. speed = 2*4*2/(4+2)
=16/6 = 8/3 = 2 2/3
avg.speed = 2ab/(a+b), where a and b are the respective speeds.
Avg. speed = 2*4*2/(4+2)
=16/6 = 8/3 = 2 2/3
