Quantitative Aptitude Ques 2257
Question: When a person cycled at 10 km/h, he arrived at his office 6 min late. He arrived 6 min early, when he increased his speed by 12 km/h. The distance of his office from the starting place is
Options:
A) 6 km
B) 7 km
C) 12 km
D) 16 km
Show Answer
Answer:
Correct Answer: C
Solution:
- Let the distance be D km, and actual time taken by man to reached the office at time = x
According to the question,
$ \frac{D}{10}=x+\frac{6}{60} $
(i)
and $ \frac{D}{12}=x-\frac{6}{60} $
(ii)
From Eqs (i) and (ii), we get
$ \frac{D}{10}-\frac{D}{12}=x+\frac{6}{60}-x+\frac{6}{60} $
$ \frac{12D-10D}{120}=\frac{1}{10}+\frac{1}{10} $
$ \Rightarrow $ $ \frac{2D}{120}=\frac{2}{D}=12,km $
Alternate Method
Here, $ b _1=6, $ $ t _2=6, $ $ S _1=10 $ and $ S _2=12 $
Distance $ =\frac{(t _1+t _2)S _1,.,S _2}{(S _2-S _1)\times 60}=\frac{(6+6),10\times 12}{(12-10)\times 60} $
$ =\frac{12\times 120}{2\times 60}=\frac{24}{2}=12,km $