Boats and Streams | Arithmetic aptitude | Discussion Page

The speed of a motor boat to that of the current of water is 36 : 5. The boat goes along with the current in 5 hours 10 minutes. It will come back in

A) 5 hrs 50 mts

B) 6 hrs

C) 6 hrs 50 mts

D) 12 hrs 10 mts

E) 10 hrs 10 mts

Option C

Let speed of motor boat $= 36x$ km/hr

Speed of current $= 5x$ km/hr

The boat goes along with the current in $\frac{31}{6}$ hrs (5 hrs 10 mins)

Distance $=\left({\frac{31}{6}}\times (36x + 5x)\right)$ $=\frac{(41x\times 31)}{6}$

Rate upstream $=36x-5x$ $=31x$

Time taken $=\left(\frac{41x\times\frac{31}{6}}{31x}\right)$ $=\frac{41}{6}$ hrs = 6 hrs 50 minutes.

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