A boat goes 100 km downstream in 8 hours, and 75 Km upstream in 15 hours. The speed of the stream is?  Choose one
A) 3
B) 6.5
C) 5.5
D) 4
E) 3.75

Rationale: "100 - - - 10 ds = 12.5 ? - - - - 1 75 - - - - 15 us = 5 ? - - - - - 1 s = ( 12.5 - 5 ) / 2 = 3.75 kmph . answer : e"
Answer: E