Question

A boat, while going down-stream in a river covered a distance of 50 miles at an average speed of 60 miles per hour. While returning, because of the water resistance, it took one hour fifteen minutes to cover the same distance. What was the average speed during the whole journey?

• A. 40mph
• B. 48 mph
• C. 50 mph
• D. 55 mph

Answer 1

Answer: (B)

48 mph

Answer 2

Time taken by boat to go downstream =$\frac{50}{60}=\frac{5}{6}$hours
Time taken for upstream distance =$1+\frac{1}{4}=\frac{5}{4}$ hours
Total time =$\frac{5}{6}+\frac{5}{4}=\frac{25}{12}$ hours and total distance covered =$50+50=100$ miles
Therefore, Average speed = total distance/total time
=$\frac{\frac{100}{25}}{12}=48$ mph
The correct answer is (B) : 48 mph