Aptitude Discussion

Q. |
Ram covers a part of the journey at 20 kmph and the balance at 70 kmph taking total of 8 hours to cover the distance of 400 km. How many hours has he been driving at 20 kmph? |

✖ A. |
2 hours |

✖ B. |
3 hours 20 minutes |

✖ C. |
4 hours 40 minutes |

✔ D. |
3 hours 12 minutes |

**Solution:**

Option(**D**) is correct

Let $x$ be the number of hours he travels at 20 kmph.

Distance covered in this x hours = $20x$ km

He would have therefore, travelled the balance $(8–x)$ hours at 70 kmph.

Distance covered in this $8–x$ hours = $(8−x)×70=(560–70x)$ km

The total distance travelled = $20x+560–70x = 400$

$⇒160=50x$

\(â‡’x=\left(\dfrac{160}{50}\right)\) hours

= 3.2 hours

= **3 hours and 12 minutes**

**Aditya Pant**

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**Vaibhav Gupta**

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Alternate solution:

Let he travels x hours @20 kmph and y hours @70kmph

Then, x+y=8..….....…...(1)

Also,20x+70y=400......(2) [Distance travelled@20 kmph+Distance travelled@70kmph]

Solving for x we get x=3.2 i.e. 3hours12minutes

(As 0.2 hour means 2/10×60=12 minutes)

it is better to go through the option elimination method in this type.