Question

The Dallas train passes a 200 m long platform in just 40 seconds and a static pole in 25 seconds. Find the approximate length of the train.
A. O 323 m
B. O 333 m
O 313 m
D. O 300 m

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Answer 1

Step-by-step explanation:

Let the length of the train be 'l', and the speed of the train be 's'.

First given: When the train passes the 200 m long platform in 40 seconds:

$speeed = \frac{distance}{time}$

In this case, the total distance is (200+l) meters.

Therefore,

$s = \frac{200 + l}{40}$

200 + l = 40s

40s - l = 200 ------------ (1)

2. Second given is that the train passes a static pole in 25 seconds:

Distance = l

Speed = s

Time = 25 seconds

Therefore,

$s = \frac{l}{25}$

l = 25 s

25s - l = 0 --------------- (2)

Now solve equations (1) and (2) simultaneously:

40s - l = 200

25s - l = 0

40s - l = 200 (3)

-25s + l = 0 (4)

Add equations (3) and (4):

15s = 200

$s = \frac{200}{15} meter \: per \: second$

Substitute by s = 200/15 in equation (2):

$25 \times \frac{200}{15} - l = 0$

L = 333.33m