In a km race, A gives B a start of 20 seconds and beats him by 40m. However, when he gives B a start of 25 seconds they finish in a dead heat. What is A’s speed in m/sec?
(1)
12.5 m/sec
(2)
20 m/sec
(3)
8 m/sec
(4)
10 m/sec
Correct Answer - (4)
Solution
A gives B a start of 20 seconds and beats him by 40m in the first race. But when A gives B 25 seconds start, they end in a dead heat.
The extra 5 seconds that A gives B compensates for the 40 m. Therefore, in 5 seconds, B runs 40m. Therefore, speed of B = = 8m/sec.
Running at 8 m/sec B will take = 125 seconds to complete the 1000 meters. As A gives B a start of 25 seconds to finish the race in a dead heat, A will take 125 - 25 = 100 seconds to complete the race.
Therefore, A’s speed = = 10 m/sec.
= 8m/sec.
= 125 seconds to complete the 1000 meters. As A gives B a start of 25 seconds to finish the race in a dead heat, A will take 125 - 25 = 100 seconds to complete the race.
= 10 m/sec.