Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 31)
31.
Two, trains, one from Howrah to Patna and the other from Patna to Howrah, start simultaneously. After they meet, the trains reach their destinations after 9 hours and 16 hours respectively. The ratio of their speeds is:
Answer: Option
Explanation:
Let us name the trains as A and B. Then,
(A's speed) : (B's speed) = b : a = 16 : 9 = 4 : 3.
Discussion:
108 comments Page 2 of 11.
Vijay said:
1 decade ago
Ishita Narula z correct....
Abhimanini said:
1 decade ago
How can we calculate the time to cover the total distance, for this sum?
Subhendu said:
1 decade ago
@abhisek.
Please be reasonable yaar. Otherwise you will be a laughing stuff to everyone.
Please be reasonable yaar. Otherwise you will be a laughing stuff to everyone.
Pradeep vishwakarma said:
1 decade ago
Ishita narula is correct. Thank you.
Himanshu said:
1 decade ago
One of the smart way of doing the question is by seeing the options itself. Since the first train reach its destination earliest after meeting the second train, then its speed would be greater than the second train and so as the ratio. In the options given above, only in B the ratio of the first train greater than the second.
Pawan said:
1 decade ago
Hello please solve this question.
The speed of a train is 90 kmphr, how much distance will it cover in 4 hr 40 min.
The speed of a train is 90 kmphr, how much distance will it cover in 4 hr 40 min.
Sundar said:
1 decade ago
@Pawan :
Detailed explanation:
---------------------
Formula: Distance = (Speed x Time).
Speed = 90 km/hr
Convert km/hr into m/sec.
Therefore, Speed = (90 x 1000/3600) = 90000/3600 = 25 m/s
Now, Time = 4 hr 40 min
Convert it into secs.
Therefore = (4 x 3600) + (40 x 60 )= 14400+2400 = 16800 secs.
Now, Distance = 25 m/sec x 16800 sec = 25 x 16800 m
= 4,20,000 m [or]
= 420 km. [1000 m = 1 km]
Some short-cut tricks :
-----------------------
Distance = (Speed x Time)
We can write 4 hr 40 mins = (4 + 40/60) hrs.
So, Distance = 90 x (4 + 2/3)
= (90 x 4) + (90 x 2/3)
= 360 + 60
= 420 km. [or] 420000 m.
Detailed explanation:
---------------------
Formula: Distance = (Speed x Time).
Speed = 90 km/hr
Convert km/hr into m/sec.
Therefore, Speed = (90 x 1000/3600) = 90000/3600 = 25 m/s
Now, Time = 4 hr 40 min
Convert it into secs.
Therefore = (4 x 3600) + (40 x 60 )= 14400+2400 = 16800 secs.
Now, Distance = 25 m/sec x 16800 sec = 25 x 16800 m
= 4,20,000 m [or]
= 420 km. [1000 m = 1 km]
Some short-cut tricks :
-----------------------
Distance = (Speed x Time)
We can write 4 hr 40 mins = (4 + 40/60) hrs.
So, Distance = 90 x (4 + 2/3)
= (90 x 4) + (90 x 2/3)
= 360 + 60
= 420 km. [or] 420000 m.
Dheeraj said:
1 decade ago
(A's Speed):(B's Speed)= sq.under root a: sq.under root b
Sudipto Maity said:
1 decade ago
Good Problem !!!Just memorize the FORMULA .
Ishaq Ahamed said:
1 decade ago
d1+d2= D;(total distance)
v1=d1/t1; =>v1=(D-d2)/t1----> EQ1
v2=d2/t2; => v2=(D-d1)/t2---->EQ2
d1 is distance traveled by first train to meet the 2nd, similarly d2 is distance traveled by second train to meet first train;
t1 is time taken by train 1 to meet the other
t2 is time taken by train 2 to meet first train
now d1+d2= D;(total distance)
according to given data
v1=(D-d1)/9;
v2=(D-d2)/16;
v1/v2=(16/9) *((D-d1)/(D-d2));
=(16/9) *((v2/t2)/(v1/t1))----->from EQ1 and EQ2
(v1/v2)^2 =(16/9)(t1/t2)
t1 and t2 are equal as trains start at same time and both meet after equal amounts of time so, memorize the above formula
v1=d1/t1; =>v1=(D-d2)/t1----> EQ1
v2=d2/t2; => v2=(D-d1)/t2---->EQ2
d1 is distance traveled by first train to meet the 2nd, similarly d2 is distance traveled by second train to meet first train;
t1 is time taken by train 1 to meet the other
t2 is time taken by train 2 to meet first train
now d1+d2= D;(total distance)
according to given data
v1=(D-d1)/9;
v2=(D-d2)/16;
v1/v2=(16/9) *((D-d1)/(D-d2));
=(16/9) *((v2/t2)/(v1/t1))----->from EQ1 and EQ2
(v1/v2)^2 =(16/9)(t1/t2)
t1 and t2 are equal as trains start at same time and both meet after equal amounts of time so, memorize the above formula
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