Aptitude Discussion

Q. |
A boatman rows to a place 45 km distant and back in 20 hour. He finds that he can row 12 km with the stream in the same time as 4 km against the stream. Find the speed of the stream. |

✔ A. |
3 km/hr |

✖ B. |
2.5 km/hr |

✖ C. |
4 km/hr |

✖ D. |
3.5 km/hr |

**Solution:**

Option(**A**) is correct

Ratio of time taken for up and down = $3:1$

Out of 20 hr he took 15 hr for up and 5 for down.

Speed up = \(\dfrac{45}{15}=3\)

and down = \(\dfrac{45}{5}=9\)

Hence speed of stream

= \((9âˆ’3)\times \dfrac{1}{2}\)

= **3 km/hr**

**Pratima**

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**NerdBird**

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Was it supposed to be (9-3) x 1/2?

How is the ratio found out?