Practice Test Discussion

A person covers 9 km with a speed of 3 km/hr. 25 km with a speed of 5 km/hr and 30 km with a speed of 10 km/hr. Find out the average speed of person?

$11 \frac{5}{9} km / hr$

$9 \frac{5}{11} km / hr$

56 km/hr

$5 \frac{9}{11} km / hr$

None of these

Explanation

Given,

P= 9 km/hr, Q=25 km, R=30 km

X= 3 km/hr, Y =5 km/hr, Z=10 km/hr

∴ Required average speed $= \frac{P + Q + R}{\frac{P}{X} + \frac{Q}{Y} + \frac{R}{Z}}$

$= \frac{9 + 25 + 30}{\frac{9}{3} + \frac{25}{5} + \frac{30}{10}} = \frac{64}{3 + 5 + 3} = \frac{64}{11} = 5 \frac{9}{11} km / hr$

Hence, Option D is correct.

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