A man's speed with the current is 21 km/hr and the speed of the current is 4.3 km/hr. The man's speed against the current is Options:
A) 9.2  B) 10.3  C) 11.5  D) 12.4  E) 13

Rationale: "man ' s rate in still water = ( 21 - 4.3 ) km / hr = 16.7 km / hr . man ' s rate against the current = ( 16.7 - 4.3 ) km / hr = 12.4 km / hr . answer : d"
Answer: D