Question 89

A and B take part in a 100 m race. A runs at 5 km/hr. A gives B a start of 8 m and still beats him by 8seconds. Find the speed of B.

Solution

A's speed$$=(5\times\frac{5}{18})m/\sec=\frac{25}{18}m/\sec.$$

Time taken by A to cover 100 m $$=(100\times\frac{18}{25})\sec=72\sec.$$

Time taken by B to cover 92 m = (72 + 8) = 80 sec.

B's speed $$=\frac{92}{80}\times\frac{18}{5}\ kmph=4.14kmph.$$

A is correct choice.

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