Time, Speed & Distance
Aptitude

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Q.

A bus without stopping travels at an average speed of 60 km/hr and with stoppages at an average speed of 40 km/hr. What is the total time taken by the bus for stoppages on a route of length 300km?

 A.

4 hr

 B.

3 hr

 C.

2.5 hr

 D.

3.5 hr

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Solution:
Option(C) is correct

Let $r$ = running time of the train

$s$= stoppage time of the train

$D$= total distance travelled by train

We have:

\(\dfrac{D}{r}=60\text{ and }\dfrac{D}{r+s}=40\)

\(\Rightarrow \dfrac{r+s}{r}=\dfrac{3}{2}\)

\(\Rightarrow \dfrac{s}{r}=\dfrac{1}{2}\)

As, $D=300$ kms

\(\dfrac{300}{r}=60\)

$⇒ r=5$ hrs and $s$ = 2.5 hr

Edit: For an alternative solution, check comment by Zoha Amjad.


(2) Comment(s)


Achin
 ()

ShortCut:

Time taken by bus to go nonstop=300/60=5Hr

Time taken by bus to go with stoppages=300/40=7.5Hr

Extra time =7.5-5.0=2.5

Bus takes 2.5 hours for stoppages.



Zoha Amjad
 ()

Time when speed in 60 km/hr

$t= \dfrac{300}{60} = 5$ hrs

Time when speed is 40 km/hr

$t= \dfrac{300}{40} = 7.5$

Now the difference in time will be the total time taken on stoppages,

$=7.5-5 = \textbf{2.5 hrs}$