Gujarati
Hindi
4.Average
hard

The average speed of a train running at a speed of $30\, km / h$ during the first $100\, kilometres,$ at $40\, km / h$ during the second $100\, kilometres$ and at $50\,km / h$ during the last $100\, kilometres$ is nearly (in $km/h$)

A

$38.5$

B

$38.3$

C

$40.0$

D

$39.2$

Solution

Time taken to cover first $100\, kilometres$

$=\frac{100}{30}=3 \frac{1}{3} hrs$

Time taken to cover second $100 \,kilometres$

$=\frac{100}{40}=2 \frac{1}{2} hrs$

Time take to cover last $100 \,kilometres$

$=\frac{100}{50}=2 \,hrs$

Total time taken $=3 \frac{1}{3}+2 \frac{1}{2}+2=\frac{10}{3}+\frac{5}{2}+2$

$=\frac{47}{6} h$

Total distance covered $=300 \,km$

$\therefore \quad$ Average speed $=\frac{300}{47 / 6}=\frac{300 \times 6}{47}=38.3 km / h$

Standard 13
Quantitative Aptitude

Similar Questions

Start a Free Trial Now

Confusing about what to choose? Our team will schedule a demo shortly.