Pls answer the question. Two men are running in the same direction with
speeds of 6 km per hour and 75 km per respec-
tively. A train running in the same direction crosses
1
them in 5 sec and 55 sec respectively. The length
2
and the speed of the train are respectively.
(a) 22.92 m (approximately) and 22 km per hour
(b) 22 m (approximately) and 22.5 km per hour
(c) 22.90 m (approximately) and 20.5 km per hour
(d) 22.92 m (approximately) and 22.5 km per hour
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Verified answer
Answer:
Let the length of the train be l m and its speed be x km/hr
Then relative speed of train w.r.t. 1
st
man
=(x−6) km/hr
=(x−6)×
18
5
m/s
Relative speed of train w.r.t 2
nd
man =(x−7.5) km/hr = (x−7.5)×
18
5
m/s
Length of the train = Distance travelled in both the cases
⇒(x−6)×
18
5
×5=(x−7.5)×
18
5
×5.5
⇒(x−6)×5=(x−7.5)×5.5
⇒5x−30=5.5x−41.25
⇒0.5x=11.25
⇒x=
0.5
11.25
=22.5 km/hr
∴ Length of the train = ((22.5−6)×
18
5
×5)m=22.92 m (approx).