ANS:A - 45 m
2 kmph = |
 |
2 x |
5 |
 |
m/sec = |
5 |
m/sec. |
18 |
9 |
4 kmph = |
 |
4 x |
5 |
 |
m/sec = |
10 |
m/sec. |
18 |
9 |
Let the length of the train be
x metres and its speed by
y m/sec.

9
y - 5 =
x and 10(9
y - 10) = 9
x

9
y -
x = 5 and 90
y - 9
x = 100.
On solving, we get:
x = 50.

Length of the train is 50 m.