Aptitude - Time and Distance - Discussion
Discussion Forum : Time and Distance - General Questions (Q.No. 13)
13.
It takes eight hours for a 600 km journey, if 120 km is done by train and the rest by car. It takes 20 minutes more, if 200 km is done by train and the rest by car. The ratio of the speed of the train to that of the cars is:
Answer: Option
Explanation:
Let the speed of the train be x km/hr and that of the car be y km/hr.
| Then, | 120 | + | 480 | = 8  |
1 | + | 4 | = | 1 | ....(i) |
| x | y | x | y | 15 |
| And, | 200 | + | 400 | = | 25 | |
1 | + | 2 | = | 1 | ....(ii) |
| x | y | 3 | x | y | 24 |
Solving (i) and (ii), we get: x = 60 and y = 80.
Ratio of speeds = 60 : 80 = 3 : 4.
Discussion:
84 comments Page 4 of 9.
Monika said:
8 years ago
Thanks @Ophi.
Pradeep said:
9 years ago
In first equation divide both sides by 120 then we get 1/15.
120/x + 480/y = 8,
1/x + 4/y = 8/120,
= 1/15.
120/x + 480/y = 8,
1/x + 4/y = 8/120,
= 1/15.
Liton das said:
8 years ago
25/3 how did it convert to 1/24?
Please explain.
Please explain.
ID.PRASAD said:
8 years ago
@Liton Das.
200/x +400/y = 25/3,
Now, 200 common.
200 (1/x+2/y) = 25/3.
(1/x+2/y) = (25/3) * (1/200),
After the cancellation,
We get,
(1/x+2/y) = 1/24,
Got it.
200/x +400/y = 25/3,
Now, 200 common.
200 (1/x+2/y) = 25/3.
(1/x+2/y) = (25/3) * (1/200),
After the cancellation,
We get,
(1/x+2/y) = 1/24,
Got it.
Dhirendra mehta said:
8 years ago
How comes 3?
Chandu Balaji said:
8 years ago
Can we use alligation method here. Please clarify my doubt?
Siddhant ojha said:
8 years ago
The solution given is not right because of 8+2/3=26/3 not 25/3.
Gopalakrishnan said:
4 years ago
Thanks @Ophi
Vikash said:
9 years ago
Change 20 min in an hour then add 8 because take more time we get 25/3.
D.Rajkumar said:
7 years ago
The second one takes 20 minute more then time is 8:20 but 25/3 is 8.3.
So, 33/4 is 8.2 is correct
So, 33/4 is 8.2 is correct
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