A train started at 9.00 am from station X with a speed of 72 km/h. After two hours, another train started from Y towards X with a speed of 90 km/h. The two trains are expected to cross each other at 1.30 P. M. Owing to a signal problem arising at 12 noon, the speed of each of them was reduced by the same quantity and they cross each other at 4.30 P. M. Q38. What is the new speed of the trains that started from station X? Q39. If the signal problem had occurred at 1.00 P.M. instead of 12 noon, at what time would the two trains have crossed each other? |
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Q38. What is the new speed of the trains that started from station X?
a. 18 km/h
b. 36 km/h
c. 45 km/h
d. 54 km/h
if reduced speed =x
so 3*72+4.5(72-x)+90+4.5(90-x)=549
sox=54 so ans =18
Little Star
n/a
Q39. If the signal problem had occurred at 1.00 P.M. instead of 12 noon, at what time would the two trains have crossed each other?
a. 3.30 P.M.
b. 3.00 P.M
c. 2.00 P.M
d. 2.30 P. M
ans is (d) 2:30pm
Little Star
n/a
Can somebody expalin the solution to these two qs. I am also stuck in these.
A train started at 9.00 am from station X with a speed of 72 km/h. After two hours, another train started from Y towards X with a speed of 90 km/h. The two trains are expected to cross each other at 1.30 P. M. Owing to a signal problem arising at 12 noon, the speed of each of them was reduced by the same quantity and they cross each other at 4.30 P. M.
Q38. What is the new speed of the trains that started from station X?
a. 18 km/h
b. 36 km/h
c. 45 km/h
d. 54 km/h
Q39. If the signal problem had occurred at 1.00 P.M. instead of 12 noon, at what time would the two trains have crossed each other?
a. 3.30 P.M.
b. 3.00 P.M
c. 2.00 P.M
d. 2.30 P. M
Ans : Let the trains meet at point P
Distance travelled by train that started from station X = 72*4.5
= 324 km
So XP= 324 km
Distance travelled by train that started from station Y =90*2.5
=225 km
so YP =225 km
Total Distance= XY=XP+YP=549 km
38: Let the speed b reduced by x km/hr.
Total Distance will remain same
So, 72*3+ (72-x)*4.5+ 90+ (90-x)4.5=549
This gives x=54km/hr
So new speeds of the trains that started from station X & Y r respectively 18 & 36 km/hr
39:Let x hours b the time taken after signal problem occurs (i.e. at 1.00 pm).
Now the speeds of trains after signal problem occurs is 18 & 36 km/hr (as derived above)
Again, Total Distance will remain same
So,
72*4+18*x +90*2 +36*x=549
x= 1.5 hours
So, the two trains cross each other 1.5 hours after signal problem occurs i.e. at 2:30 pm.
18
n/a
2.30pm
n/a
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