SSC CGL Tier II 25 Oct 2015 Paper 1

Question : 42 of 100

Marks: +1, -0

A car covers four successive 7 km distances at speeds of 10 km/hour, 20 km/hour, 30 km/ hour and 60 km/hour respectively. Its average speed over this distance is

30 km/hour
20 km/hour
60 km/hour
40 km/hour

Validate

Solution:

(2) Total distance = 7 × 4 = 28 km.
Total time

= ( {7}/{10}+ {7}/{20}+ {7}/{30}+ {7}/{60} )

hours

=({42+21+14+7}/60)

hours

=84/60

hours

=7/5

hours
∴ Average speed

= { { \Total \distance }}/{ { \Total \time }}= ( {28}/{ {7}/{5}} ) {\kmph}

= {28 × 5}/{7}=20 {\kmph}

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