Mathematics
Medium
Question
A car travels 100 km at a speed of 60 km/h and returns with a speed of 40 km/h. Calculate the average speed for the whole journey.
(A) 40 km/h
(B) 44 km/h
(C) 48 km/h
(D) 52 km/h
A
40 km/h
B
44 km/h
C
48 km/h
✓ Official correct answer
D
52 km/h
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A
40 km/h
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B
44 km/h
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C
48 km/h
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D
52 km/h
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Explanation
Solution
Time taken to cover 100 km = distance/speed = 100/60 = 1.66
Time taken to return back = 100/40 = 2.5
Average speed = total distance/total time = (100+100)/(1.66+2.5) = 200/4.16 = 48 km/h
Time taken to cover 100 km = distance/speed = 100/60 = 1.66
Time taken to return back = 100/40 = 2.5
Average speed = total distance/total time = (100+100)/(1.66+2.5) = 200/4.16 = 48 km/h