If the ratio of the speed of a boat in downstream and the speed of the stream is 10 : 1. If the boat

M4maths Previous Puzzles

10 Mar 2022 Boat and Streams

If the ratio of the speed of a boat in downstream and the speed of the stream is 10 : 1. If the boat can travel 320 km upstream in 20 hours then find the total distance travelled (in km) by the boat in still water in the same time?

OPtion

1) 320
2) 400
3) 420
4) 300
5) 360
6) 480
7) 520
8) 600
9) 720
10) None of these

Solution

Let the speed of boat in downstream = 10x km/hr and the speed of the stream = x km/hr
Upstream speed = 320/20 = 16 km/hr
Let the speed of boat in still water = b km/hr
Then, b - x = 16 ----(i)
Also, downstream speed = b + x = 10x => b = 9x
Substituting value of b in Eqn (i), we get 8x = 16 or x=2 km/hr.
From (i), Speed of the boat b = x + 16 = 18 km/hr
.'. Distance travelled by boat in 20 hours in still water = 20*b = 20*18 = 360 km.

Correct Option: 5 Best Solution (1)

G.S.Kantharao   2 years AGO

Ratio of speeds of down stream and stream=10:1
Let Speeds of Boat and Stream are X,Y
Given X+Y:Y=10:1
Now X:Y=9:1
Speeds of up and down streams=(9+1):(9-1)=10:8
It took 20hrs for 320Km in up stream means
9:1=D:320/8
=>Distance it travelled in still water= 9*40=360Km.
My option is 5👈

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