Practice | Hashtable

1. In a 800 metre race, A defeated B by 15 seconds. If A's speed was 8 km/hr, the speed of B was -

A. $\frac{16}{27} km / hr$

B. $\frac{27}{16} km / hr$

C. $7 \frac{17}{25} km / hr$

D. $8 \frac{17}{25} km / hr$

Solution:

A's speed
= 8 km/hr
=

(8 \times \frac{5}{18})

m/sec
=

\frac{20}{9}

m/sec
Time taken by A to cover 800 m
=

(800 \times \frac{9}{20})

sec
= 360 sec
Time taken by B to cover 800 m
= (360 + 15) sec
= 375 sec
∴ Speed of B :
=

\frac{800}{375}

m/sec
=

(\frac{800}{375} \times \frac{18}{5})

km/hr
=

\frac{192}{25}

km/hr
=

7 \frac{17}{25}

km/hr

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