A motor boat in still water travels at a speed of 36kmph. It goes 56 km upstream in 1 hour 45 min. The time taken by it to travel the same downstream is

# A motor boat in still water travels at a speed of 36kmph. It goes 56 km upstream in 1 hour 45 min. The time taken by it to travel the same downstream is

1. A
2 hr 25 min
2. B
3 hr
3. C
1 hr 24 min
4. D
2 hr 21 min

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### Solution:

Speed upstream $=\frac{56\text{km}}{1\frac{3}{4}\text{hr}}$

$=\frac{56×4}{7}=32\text{kmph}$

Let the speed of the current be $x$ kmph

$\therefore 36-x=32$

$x=36-32=4\text{kmph}$

Speed downstream $=36+4=40\text{kmph}$

$\therefore$ Taken downstream $=\frac{56}{40}=\frac{7}{5}\text{hrs}$

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