Three-fifth of a journey is covered at a speed of 84 km/hr, and the remaining distance is covered at the rate of 56 km/hr. The average speed for the whole journey (in km/hr) is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 70.
Let total distance = 420 km
Distance1 = 3/5 × 420 = 252 km
Time1 = 252 ÷ 84 = 3 hr
Distance2 = 168 km at 56 km/hr
Time2 = 168 ÷ 56 = 3 hr
Total time = 3 + 3 = 6 hr
Average speed = 420 ÷ 6 = 70 km/hr