Two trains for Mumbai leave Delhi at 6 am and 6.45 am and travel at 100 kmph and 136 kmph respectively. How many kilometers from Delhi will the two trains be together:
A. 262.4 km
B. 260 km
C. 283.33 km
D. 275 km
E. None of these
Answer: Option C
Solution(By Examveda Team)
Difference in time of departure between two trains = 45 min. = $$\frac{{45}}{{60}}$$ hour = $$\frac{{3}}{{4}}$$ hour. Let the distance be x km from Delhi where the two trains will be together. Time taken to cover x km with speed 136 kmph be t hour and time taken to cover x km with speed 100 kmph (As the train take 45 mins. more) be $$ {{\text{t}} + \frac{3}{4}} $$ = $$ {\frac{{4{\text{t}} + 3}}{4}} $$ Now, 100 × $$ {\frac{{4{\text{t}} + 3}}{4}} $$ = 136t Or, 25(4t + 3) = 136t Or, 100t + 75 = 136t Or, 36t = 75 Or, t = $$\frac{{75}}{{36}}$$ = 2.083 hours Then, distance x km = 136 × 2.083 ≈ 283.33 km.Join The Discussion
Comments ( 6 )
Related Questions on Speed Time and Distance
A. 48 min.
B. 60 min.
C. 42 min.
D. 62 min.
E. 66 min.
A. 262.4 km
B. 260 km
C. 283.33 km
D. 275 km
E. None of these
A. 4 hours
B. 4 hours 30 min.
C. 4 hours 45 min.
D. 5 hours
since it is asked to find the distance they were together since delhi to let a point m where they meet. we are not asked to find the value of m or the distance from delhi to point m. correct answer will be 208.33
Why we consider time as a constant
Let A = train with speed 100kmph and
B = train with speed 136kmph
And, Let x be the distance from Delhi to the point where the two trains meet.
Then,
time take by train A = x÷100 ( time = distance÷speed)
And,
time taken by train B = x ÷ 136
Difference in time taken = 45 minutes
Now
(x÷100)-(x÷136) = 45 minutes or 3/4 hr
Solve for x
Then you will get x= 283.33 km.
This is the answer
time deference =45min.=0.75hrs
1st train go in this period=100*.75=75km
now relative speed =(136-100)=36km/hr
so 2nd train meet each other time is=75÷36=2.08
distance is=136*2.08=283.33km
Simply you can use formua
Distance= (S1*S2*T) / (S1-S2)
where T= difference in time i.e. 45 min means 3/4 hrs. , S1 and S2 are speeds of given
Already 100 kmph train started before 136kmph train. So when time is taken into point where they meet the time taken by 100kmph train should be less than the other one. But u took in this way. Can u plz explaim???