A and B run a 1 km race. A gives B a start of 50 m and still beats him by 15 seconds. If A runs at 8 km/h, what is the speed of B ?

(a)     4.4 km/h
(b)     5.4 km/h
(c)     6.4 km/h
(d)     7.4 km/h

anuarg1326 Default Asked on 21st January 2016 in Maths.
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1 Answer(s)

Answer: (4) 7.4 km/h

Explanation:-
Speed of A = 8 km/hr
Then, speed of A = 8 x 5/18
= 20/9 m/sec

Time taken by A to cover 1 km = 1000 x 9/20
= 50 x 9
= 450 sec

Therefore, time taken by B to cover (1000 – 50) m = (450 + 15) = 465 sec
So, speed of B = 950 x 18/465 x 5
= 190 x 18/465
= 7.35
= 7.4 km/hr

Then, the speed of B is 7.4 km/hr.

Hence, the correct answer is option (d) 7.4 km/h.

Anurag Mishra Professor Answered on 28th January 2016.
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