RRB NTPC Prelims Model Paper 5 with solutions

Question : 2 of 100

Marks: +1, -0

If a boy goes to school at 6 km/hr and returns home at 4 km/hr, find his average speed.

Solution:

(4) Let the distance of school from house is x km.
∴ time taken going to school

=x/6 h

,
time taken returning from
school

=x/4 h.

∴ average speed

={\text "total distance"}/{\text "total time taken"}

= {2x}/{[x/4 +x/6]}km/h

={2x}/{[3x+ 2x/12]}km/h

={2x× 12}/{5x}km/h

= 24/5km/h = 4.8 km/h

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