|
15.
|
A man can row 7 ½kmph in still water. If in a
river running at 1.5 km an hour, it takes him 50 minutes to row to a place
and back, how far off is the place?
|
|
|
·
A. 3
km
·
B. 4
km
·
C. 5
km
·
D. 6
km
|
Answer:
A.
Explanation:
Speed
downstream = (7.5 + 1.5) kmph = 9 kmph;
Speed
upstream = (7.5 - 1.5) kmph = 6 kmph.
Let
the required distance be x km. Then,
x/9
+ x/6 = 50/60 ⇔ 2x + 3x = [5/6 * 18] ⇔ 5x = 15 ⇔ x =3.
Hence,
the required distance is 3 km.
