Question
A and B take part in a 100 metres race. A runs at 5 km an hour. A gives B a start of 8 metres and still beats him by 8 seconds. The speed of B is ?
Answer: Option B
A's speed = 5 km/hr = $$\left( {5 \times \frac{5}{{18}}} \right)$$ m/sec = $$\frac{25}{18}$$ m/sec
Time taken by A to cover 100 metres= $$\left( {100 \times \frac{{18}}{{25}}} \right)$$ = 72 sec
Time taken by B to cover 92 metres = (72 + 8) sec = 80 sec
B's speed
$$\frac{92}{80}$$ m/sec = $$\left( {\frac{{92}}{{80}} \times \frac{{18}}{5}} \right)$$ km/hr = $$\frac{414}{100}$$ km/hr= 4.14 km/hr
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A's speed = 5 km/hr = $$\left( {5 \times \frac{5}{{18}}} \right)$$ m/sec = $$\frac{25}{18}$$ m/sec
Time taken by A to cover 100 metres= $$\left( {100 \times \frac{{18}}{{25}}} \right)$$ = 72 sec
Time taken by B to cover 92 metres = (72 + 8) sec = 80 sec
B's speed
$$\frac{92}{80}$$ m/sec = $$\left( {\frac{{92}}{{80}} \times \frac{{18}}{5}} \right)$$ km/hr = $$\frac{414}{100}$$ km/hr= 4.14 km/hr
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