A man's speed with the current is 15 km / hr and the speed of the current is 2.5 km / hr. The man's speed against the current is  Choose the correct choice from the following choices.
A) 8.5 km / hr B) 9 km / hr C) 10 km / hr D) 12.5 km / hr E) None
Sol.   Man's rate in still in water = (15 - 2.5) km / hr = 12.5 km / hr.   Man's rate against the current = (12.5 - 2.5) km / hr = 10 km / hr.   Answer 10 km / hr
<result>C</result>
A man's speed with the current is 15 km / hr and the speed of the current is 2.5 km / hr. The man's speed against the current is