11
– 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
1200 meter
40
A can give B (5 min – 4 1/2 min) = 30 sec start.
The distance covered by B in 5 min = 1000 m.
Distance covered in 30 sec = (1000 * 30)/300 = 100 m.
A can give B 100m start.
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1(100-1)+ 2(100-2)+…..99(100-99)
N=100
solution: N(N-1)
100(99)= 9900
Summation of 301 – summation of 99
=41550
Summation of n=((n*n+1)/2)
1972
Answer: Pile II
Marks in thrice in english as in science
so if science marks is x
then english marks = 3x
lets maths marks = y
ratio of english and maths marks is
3x/y = 3/5
=> y = 5x
and total marks = 162
3x + x + 5x = 162
x = 18 —-answer
Let the revolutins made by bigger wheel is: x
then revolution by smaller wheel will be: x+10
Now, the distance covered by both wheels will be same.
So,
7(x+10)=9x
7x+70=9x
70=2x
35=x
so distance travelled=9*35=315
or 7*45=315
c
both a and b is correct