Roshni travelled at the speed of 66 km h while going from point A to point B and returned via the sa...........

Quantitative Aptitude (CHSL) Time & distance

Roshni travelled at the speed of 66 km/h while going from point A to point B and returned via the same route at the speed of 92.4 km/h. What was Roshni’s overall average speed during the two-way journey?

This questions was previously asked in

SSC CHSL 1st June 2022 Shift-1

View All SSCCHSL Previous Year Papers

77 km/h

79.2 km/h

79 km/h

78 km/h

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Explanation:

Correct Option 1: 77 km/hr

Average speed = Total distance travelled/Total time taken
Solution
Let Roshni travelled 'd' distance with a speed of 66 km/h
and while returning she covered the same distance 'd' with the speed of 92.4km/h Total distance covered = d + d = 2d
Let the time taken by Roshni wile going and retuning be T1 and T2 respectively
By using the formula,
Time = Distance/Speed
T1 = d/66 and T2 = d/92.4
Total time taken = T1 + T2 = d/66 + d/92.4
Average speed = 2d/(T1+T2)
= 2d/(d/66+d/92.4)= 2/(1/66+1/92.4)
On solving we get average speed ≈ 77.05 km/h
The average speed of Roshni is 77km/h