Veto q&a 7 Month22 (1)

Let the speed of the train be ‘a’ m/sec
Then (a-1.25) x 84 = (a - 1.5) x 8.5
⇔8.4 a - 10.5 = 8.5a - 12.75 ⇔0.1a = 2.25
a = 22.5
⎛ 18 ⎞
∴Speed of the train = ⎜22.5×
⎟km/hr = 81 km/hr
⎝ 5 ⎠
@hang out
300
Q A train overtakes two persons who are walking in
∴ = 120
600 − 5x
the same direction in which the train is going at
18
the rate of 2 km/h and 4 km/h and passes them
120 (600 - 5x) = 5400
completely in 9 and 10 seconds respectively. The
length of the train is
⇒ 5x = 555
5 5
2 km/h
⇒ x = 111
= 2× = m/sec
18 9
Q A train over takes two person walking along a railway
⇒ 300 = 80 + 8x
track. The first one walks at 4.5 km/hr and the other
220
one walks at 5.4 km/hr. The train needs 8.4 and 8.5
⇒ x = m/sec
seconds respectively to overtake them. What is the
8
speed of the train if both the persons are walking in
⇒ 55 m/sec
the same direction of the train
2
5 5
So the speed of the second trains in
4.5 km/hr = 4.5× = 18 4
m/sec = 1.25 m/sec
⎛55 18 ⎞
km/hr = 99 km/h
5 3
⎜ × ⎟
5.4 km/hr = 5.4 × = = 1.5 m/sec
⎝ 2 5 ⎠
18 2
Q Two trains travel in opposite directions at 36 km/h
5 10
and 45 km/h and a man sitting in slower train passes 4 km/h = 4× = m/sec
18 9
the faster train in 8 seconds. The length of the faster
train is
Let the length of the train be ‘x’ meters and its speed
by ‘y’ m/sec
Relative speed = (36 + 45) km/h
x
x
5 45
Then = 9 and = 10
= 81× = m/s
⎛ 5 ⎞ ⎛ 10 ⎞
18 2
⎜y
− ⎟ ⎜y
− ⎟
⎝ 9⎠ ⎝ 9 ⎠
⎛45 ⎞
Length of the train = ⎜ × 8 ⎟ m = 180m
∴ 9y - 5 = x and 10(9y -10) = 9x
⎝ 2 ⎠
Q Two trains are running at 40 km/h and 20 km/h
9y - x = 5 and 90 y - 9x = 100
respectively in the same direction. Fast train On solving we get x = 50
completely passes a man ;sitting in the slower train ∴The length of the train is 50 m
in 5 seconds. What is the length of the fast train
Q A train 150 m long passes a km stone in 15 seconds
Relative speed = (40 - 20) km/hr = 20 × 5
18
and another train of the same length travelling in
50
opposite direction in 8 seconds. The speed of the
= m / sec
faster train is
9
Let the speed of second train be x m/sec
Length of the faster train = x5
=
9 9
Relative speed = (10 + x) m/sec
7
= 27 m
300
9 ∴ = 8
10 + x
Q Two trains, each 100 m long moving in opposite
direction, cross each other in 8 seconds. If one is
moving twice as fast the other, then the speed of
the faster train is
Let the speed of the slower train = a m/sec
Speed of the faster train = 2a m/sec
Relative speed = a + 2a = 3a m/sec
40
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March 2018