Sumit travels from his home to office at 30 km/h and reaches 12 minutes late. When he increases his speed by 10 km/h he reaches 6 minutes earlier. What is the distance between his office and home?
Sumit travels from his home to office at 30 km/h and reaches 12 minutes late. When he increases his speed by 10 km/h he reaches 6 minutes earlier. What is the distance between his office and home? Correct Answer 36 km
Given:
Initial speed(S1) = 30 km/hr
New speed(S2) = 40 km/h
Concept:
When same distance is travelled with different speeds, the ratio of time taken is the reciprocal of the ratio of respective speeds.
S1/S2 = T2/T1
Formula used:
Distance travelled = Speed × time taken
Calculation:
Let the exact time to reach office = x hrs
∴ Time taken with speed 30 km/h(T1) = (x + 12) min
Time taken with speed 40 km/h(T2) = (x - 6) min
∵ T2/T1 = S1/S2
⇒ T2/T1 = 40/30
⇒ T2/T1 = 4/3
Let T1 = 4a
T2 = 3a
∴ T1 - T2 = 4a - 3a = a
∵ T1 - T2 = x + 12 - x + 6
= 18 min
∴ a = 18 min
∴ Time taken to reach office with speed 30 km/h = 4a = 4 × 18 = 72 min = (72/60) hrs
∴ Distance between office and home = (30 km/h) × (72/60) km
= 36 km