Dewey square group Interview Questions, Process, and Tips

The correct ANS: option C

60*5/18*9=150

740

20kmph

– While the train is moving, the jogger will also be running in the same direction.
– for the head(engine) of the train to get to the current position of the jogger 240m away, it will take:
45km/hr => 12.5m/s => 240/12.5 = 19.2 seconds.

– But in the same period of time, the jogger will still be running and will have moved to a new location by: 9km/hr => 2.5m/s => 2.5 * 19.2 = 48m

To get to the new location at the speed of 12.5m/s will take the train:
48/12.5 = 3.84sec

In this additional time, the jogger will move forward by:
3.84 * 2.5 = 9.6m

at a speed of 12.5m/s, it will take the train less than a second to cover the additional 9.6m

If we add the distance the jogger will cover in 1 second to 9.6, it is still less than what the train can cover per second. let us see (9.6 + 2.5 = 12.1)

Therefore, the head of the train will pass the runner at approximately: 19.2 + 3.84 + 1 => 24.04 seconds.

For the train to completely pass the runner, it will need its whole length of 120m to be in front of the runner.

This will take an additional (9.6 + 2) seconds.

Therefore for the length of the train to be ahead of the runner it will take approx. 35.65 (24.04 + 9.6 + 2) seconds

2 urns, 9 balls.
4(2)+1=9 and 3(2)+3=9
You can’t put 4 balls in each of 7 urns with balls left over when 7*4=28. 28>24.

x

6561 → 6560/2 [-1]
3280
1640
820
410
205 [+1] =206
103 → [-1] = 102
51 [+1] = 52
26
13 [-1] = 12
6
3 [+1] 4
2
1

2.5 sec

7500

Let n be the number of days it takes A and B, working together, to finish. And we know B=A+10 and B=3A, so:

3A=A+10

2A=10

A=5

Then B=15

So:

1/A + 1/B=1/n where n is the total amount of days. So:

1/5 + 1/15=1/n

3n+n=15

n=15/4 days

B. No such pair exists