Correct Answer - Option 4 : 14 km
Given:
S1 = 3 Km/h
S2 = 4 Km/h
Time difference in hour = (40 + 30)/60 = 7/6 hour
Formula used:
Distance = S1 × S2 × Time difference / Speed difference
Calculation:
Distance = (3 × 4 × 7/6)/1 = 14 Km
∴ The distance between house and office is 14 Km.
ALTERNATE METHOD
Let the total distance be x km
We know time = distance/speed,
Time taken to travel at 3 km/hour = x/3 hour and,
Time taken to travel at 4 km/hour = x/4 hour.
Total difference in time = 40 minutes + 30 minutes = 70 minutes or 70/60 hours.
⇒ x/3 – x/4 = 70/60
⇒ x/12 = 7/6
⇒ x = 14
∴ The distance between house and office is 14 Km.