A man’s average driving speed for 9 hours is 88 km/hr. During the first five hours of his journey, he drove at 74 km/hr, and last two hours he drove at 82 km/hr. What was his average speed (in km/hr) for the sixth and the seventh hour?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e 129.
Total time = 9 hours
Average speed = 88 km/h
So, total distance = 88 × 9 = 792 km
Distance in first 5 hours at 74 km/h = 74 × 5 = 370 km
Distance in last 2 hours at 82 km/h = 82 × 2 = 164 km
Distance during 6th and 7th hour = 792 - (370 + 164) = 258 km
Time = 2 hours
Average speed for 6th and 7th hour = 258 ÷ 2 = 129 km/h