A person goes from point $P$ to point $Q$ covering $1 / 3$ of the distance with speed $10 k m / h r$ , the next $1 / 3$ of the distance at $20 k m / h r$ and the last $1 / 3$ of the distance at $60 k m / h r$ . The average speed of the person is

30 k m / h r

No worries! We‘ve got your back. Try BYJU‘S free classes today!

24 k m / h r

No worries! We‘ve got your back. Try BYJU‘S free classes today!

18 k m / h r

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

12 k m / h r

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is C $18 k m / h r$
Total distance covered be $x$ i.e. $S = x$
Time taken to travel first part, $t_{1} = \frac{x / 3}{10} = \frac{x}{30}$
Time taken to go to travel second part, $t_{2} = \frac{x / 3}{20} = \frac{x}{60}$
Time taken to go to travel third part, $t_{3} = \frac{x / 3}{60} = \frac{x}{180}$
Average speed of the person $v_{a v g} = \frac{S}{t_{1} + t_{2} + t_{3}}$
$∴$ $v_{a v g} = \frac{x}{\frac{x}{30} + \frac{x}{60} + \frac{x}{180}} = 18 k m / h r$

Suggest Corrections

Similar questions

Q. A car travel first

\frac{1}{3} r d

of the total distance at

30 km/hr

, next

\frac{1}{3} r d

of the total distance at

40 km/hr

and last

\frac{1}{3} r d

of the total distance at

24 km/hr

. It's average speed in

km/hr

for the whole Journey is

A car travels $\frac{1}{3}$ rd distance on a straight 3 road with a velocity of 10 km/hr, next $\frac{1}{3}$ rd with velocity $20 k m / h r$ and the last $\frac{1}{3}$ rd with velocity $60 k m / h r$ . What is the average velocity of the car in the whole journey?