Question: a man can swim in still water at 6 km / h , but takes twice as long to swim upstream than downstream . the speed of the stream is ?
A) 3
B) 7.5
C) 2.25
D) 2
E) 4
Correct answer: D
Grade: 6 | Topic: Ratios and proportions | Difficulty: Medium | Standard: 6.RP.A.3b