Question

A train moving two third of its normal speed reaches the destination half and hour late.what is the normal time taken

Answer 1

The common thing here is the distance the train travels.

Distance = Speed × time

Let the normal speed be v.

The normal time taken be t

The distance = v × t = vt

When the speed is 1/3 we have :

Speed = 1/3v

Time = t + 0.5

Distance = 1/3v(t + 0.5) = 1/3vt + 0.5/3v

Equating the two :

vt = 1/3vt + 0.5/3v

3vt = vt + 0.5v

3vt - vt = 0.5v

2vt = 0.5v

t = (0.5v) / (2v)

t = 0.25 hrs

= 0.25

0.25hrs is the normal time taken.

We can convert it to minutes :

0.25 × 60 = 15

= 15 minutes