Question

2. a train travelling with 130kmph crossed a cycle which travelled with a speed of 10kmph in 45 secs. Calculate length of the train.

Answer 1

!! Your question is incomplete, You should say that cycle is travelling in oppsite or with the train !!

If cycle is travelling in the direvtion of train,

$\frac{l}{130 - 10} = \frac{45}{60 \times 60} \: hours \\ l = \frac{45}{60 \times 60} \times 120 \\ l = \frac{3}{2} = 1.5 \: km = 1500 \: m$

Length of train is 1500 metres.

!! But !!

If the cycle is travelling in opposite to the direction of train,

$\frac{l}{130 + 10} = \frac{45}{60 \times 60} \: hours \\ l = \frac{45}{60 \times 60} \times 140 \\ l = \frac{35}{2} = 17.5 \: km = 17500 \: m$

Length of train will be 17500 metres.