Question

in a 800m race, A defeated B by 15 seconds. If A's speed was 8km/hour, what was B's speed

Answer 1

let the speed of A be x,
Then the speed of B is x + 15

Distance = 800m
Speed of A = 8km/hr = 2.22 m/s
Time taken = Distance by speed
= 360 seconds = 6 minutes

time taken by b = 6 min 15 sec = 375 seconds
distance = 800m
speed = distance by time
= 2.13 m/s

I dont know if the ans is right or wrong

Answer 2

speed of A = 8 km/hr= 28.8 m/sec
total distance = 800 m 
total time taken by A = 800/28.8
                                 = 27.8 seconds
total time taken by B = 42.8 seconds
speed of B = 800/42.8
                  = 18.7 m/s