Question

Example 11. A train moving with
uniform speed for a certain distance takes
6 hours less if its speed be increased by
6 km/hour. It would have taken 6 hours more,
had its speed been decreased by 4 km/hr. Find
the distance travelled of the journey and the
speed of the train.
[CBSE 2012]​

Answer 1

From formula 

D=st

given

D=(s+6)(t-4)=st-4s+6t-24.......>1

D=(s-6)(t+6)=st+6s-6t-36)......>2

from 1&2 

-4s+6t=24

6s-6t=36 .....>3

on solving 

2s=60 ==> s=30 km/h

(3)==> 6(30)-6t=36

t= 24 h

.

. . D=30(24) = 720 km

Ans: D= 720 km

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