Question

two trains start from the same teshan and move in the opposite direction at the speed of 40 km per hour and 45 km per hour respectively in how many hours will they be 315 kilometre apart​

Answer 1

Step-by-step explanation:

Let 1st train covered x distance in time t

then, distance covered by 2nd train in the same time t = 850-x

speed of 1st train = x/t

=> 80 = x/t

=> x =80t .......eq.(1)

speed of 2nd train = (850-x) / t

=> 90t = (850-x)

put the value of x from eq.(1)

=> 90t = 850 - 80t

=> 90t +80t = 850

=> 170t = 850

=> t = 850/170 = 5 hr

hence, after 5hr they are 850km apart from each.

Answer 2

$3\frac{12}{17}$ hours.

Explanation:

It is stated that,

The speed of one of the train is 40 km/hr.

The speed of the other train is 45 km/hr.

Both the trains are in opposite directions from each other.

Hence, the distance between both the trains after 1 hour will be the sum of their speeds.

∴ The distance between the trains after 1 hour = (40+45) km

                                                                              = 85 km

Hence,

The trains are apart at a distance of 85 km after 1 hour.

∴ The trains are apart at a distance of 1 km after (1/85) hour.

∴ The trains are apart at a distance of 315 km after _

(1×315/85) hours

= (63/17) hours

= $3\frac{12}{17}$ hours.

∴ After $3\frac{12}{17}$ hours the trains will be apart at a distance of 315 km from each other.