Question

Two trains a and b start simultaneously in the opposite direction from two points a and b arrive at their destination 9 and 4 hours respectively after their meeting each other. At what rate does the second train b travel if the first train travels at 80 km/hr?

Answer 1

Answer:

120 km/h

Step-by-step explanation:

In the attachment.. Hope it's helpful..

Answer 2

The speed of second train is 120 km/hr

GIVEN

Two trains A and B start simultaneously in the opposite direction from two points A and B arrive at their destination 9 and 4 hours respectively after their meeting each other.

TO FIND

Speed of the second train

SOLUTION

We can simply solve the above problem as follows;

Let train A starts from point A and Train B starts from point B.

Let the two trains meet at point C.

Speed of train A = 80 km/h

Let the speed of train B = y km/hr

Let the trains take x hours to reach at point C.

We know that,

Distance = Speed × Time.

Distance of AC = 80x km

Distance of BC = xy km

It is given that train A takes 9 hours to cover distance from C to B

Therefore,

BC = 80×9 = 720 km

Or,

xy = 720 km (equation 1)

Also, Train B takes 4 hours to cover distance from C to A.

Therefore,

AC = 4y km

Or

80x = 4y

y = 20x (Equation 2)

Putting the value of y from equation 2 to equation 1.

$x \times 20x = 720$

$20 {x}^{2} = 720$

${x}^{2} = 720 \div 20 = 36$

$x = \sqrt{36} = 6hr$

Putting the value of x in equation 2

y = 20 × 6 = 120 km/hr

Hence, The speed of second train is 120 km/hr

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