1.  Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is:
A. 20 hours
B. 18 hours
C. 16 hours
D. 24 hours

Answer: Option D

Explanation:

Speed upstream = 7.5 kmph.

Speed downstream = 10.5 kmph.

Total time taken = 105 + 105 hours
7.5 10.5

= 24 hours.