A man travels by his office bus at the speed of 54 km/h and reaches 18 minutes early. If he goes at the speed of 36 km/h, he reaches 18 minutes late. What will be the speed of the bus to reach at normal time?
A man travels by his office bus at the speed of 54 km/h and reaches 18 minutes early. If he goes at the speed of 36 km/h, he reaches 18 minutes late. What will be the speed of the bus to reach at normal time? Correct Answer 216/5 km/h
Given:
Speed of bus before = 54 km/h
Speed of bus after = 36 km/h
Concept:
Speed = Distance/Time
Calculation:
Let be assume distance is D and time is T
Before
⇒ T - 18/60 = D/54 ---(1)
After
⇒ T + 18/60 = D/36 ---(2)
⇒ By equation (1) and (2)
⇒ 54 × (T - 18/60) = 36 × (T - 18/60)
⇒ 6T - 18/10 = 4T - 18/15
⇒ 2T = 18/10 - 18/15 = 18 × (1/10 - 1/15) = 18 × (3 + 2)/(30) = 90/30 = 3
⇒ T = 3/2
⇒ D = (3/2 - 18/60) × 54 = {(90 - 18)/60} × 54 = (72 × 54)/60 = 648/10
⇒ The original speed of bus = (648/10) ÷ (3/2) = (648/10) × (2/3) = 216/5 km/h
∴ The required result will be 216/5 km/h.