Aptitude - Time and Distance - Discussion

Excluding stoppages= (difference of speeds/excluding Stoppage) *60mins.

= (54-45/54) *60mins.

= (9/54) *60mins.

= (1/6) *60mins.

=10mins.

Here speed is given - 54 (excluding stoppages), 45(including ).

Time taken at stoppages -d/t.

So 9 kmph, distance - 9*60.

540/54 because (distance /time), we got 10min.

Let for a hrs, bus runs at 54 kmph.

And b hrs, bus runs at 0 kmph.

So avg speed => 45=(54*a)/(a+b).
=> a=5b.

Since we need for 1 hour;
a+b=1 hr.

We got ; b=1/6 hr stoppage time = 10 mins.

Why it use 54 km/hr with 9 km not use the 45 km/hr?

1hr----- 54 km without stoppage.

1hr----- 45 km with stoppage.

Speed = 54 km/hr.

Bus losses (54-45=) 9 km in 1hr.

Time = distance/speed.

= 9 km/54 km/hr.

= 9*60/54.

= 10 min.

Bus needs 10 min. To travel 9 km. So it losses 10 min to travel 9 km per hour.

Why should we use 54 rather than 45?

@Chandini.

Because:

Actual speed of the bus is 54 km(in 1 hour), So Due to the stops it will reduce As 45. To calculate 1 min bus traveled distance using only the actual speed (54). If We take 45 means the bus already stopped.

Because @Chandini bus is going on 54 km without stopped and 45 is this stopped time the bus that why here when the bus stopped then bus is loss a time.

0.9 km per minute, what it implies about? lost distance or no.of stoppages?

As speed of bus without stoppage is 54 kms per hour (i.e) in 1 hr bus travels 54 kms.(as Distance = speed *time).

Similarly as speed of bus with stoppage is 45 kms per hour (i.e)in 1 hr bus travels 45 kms(as Distance = speed *time).

Comparing the cases we can see that bus with stoppage covers 9 km less than the bus without stoppages.

Now we know that bus covers,

54 kms in 60 mins (1 hr)
1km in 60/54 mins
9 kms ---------------------- 60/54*9 = 10mins.

So with original speed of 54 km/h, bus stops for 10 mins.