If a man increase his speed by 6 km/hr, he cover a certain distance 4 hours earlier than the usual time and if he reduce his speed by 6 km/hr, he takes 6 hours more to cover the same distance. Find the distance.
Answer & explanation
Correct answer: option 1
Let the original speed is S km/h & time taken to cover the distance TR
ATQ, D = S × T
(S+6) (T-4) = ST
ST + 6T - 4S - 24 = ST
6T = 4S + 24 ------- (i)
(S-6) (T+6) = ST
ST + 6S - 6T - 36 = ST
6T = 6S - 36 ----- (ii)
From eqn (i) & eqn (ii)
4S + 24 = 6S - 36
2S = 60
⇒ S = 30 km/h
From eqn (i)
6T = 4S + 24
6T = 4 × 30 + 24
6T = 144
T = 24 hours
Distance = speed × time
30 × 24 = 720 km