A boatman rows upstream from point X after 28 seconds he rows back towards point X and in 28 seconds he reaches at point Y. If distance between X and Y is 784 meters, find speed of current?
OPtion
1) 10 m/s
2) 14 m/s
3) 12 m/s
4) 18 m/s
5) 21 m/s
6) 8 m/s
7) 6 m/s
8) 9 m/s
9) 7 m/s
10) None of these
Solution
X -------- (28 sec) Upstream ----------
Y -----------(784 m)----------- X
-------------------------------(28 sec) Downstream --------------------
Let speed of the boat in still water=a m/s and speed of stream=b m/s
Distance covered in downstream in 28 sec - Distance covered in upstream in 28 sec = 784 meters
⇒ (a+b)*28 - (a-b)*28 = 784
28a + 28b - 28a + 28b = 784
56b = 784
b = 14 m/s
Correct Option 2)