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 6 of 9.
Siri said:
10 years ago
I can't understand to 1/x +4/y =1/15 and 1/x +2/y =1st/24 why they take addition in this step?
Malathi said:
1 decade ago
Hai sir where we get 1/15 and 1/24?
Malathi p said:
1 decade ago
Hi, from where that 25/3 came? Please clarify my doubt sir.
Sara said:
1 decade ago
Hi @Manisha.
8 is from question see (takes 20 minutes more) than 8 hrs.
So 2 train take 8 hrs 20 minutes.
8 in hour 20 in minutes so convert 20 to hour 20/60.
8(20/60) got it?
8 is from question see (takes 20 minutes more) than 8 hrs.
So 2 train take 8 hrs 20 minutes.
8 in hour 20 in minutes so convert 20 to hour 20/60.
8(20/60) got it?
Manisha said:
1 decade ago
How this 8 value came in equation any one can you please explain?
Rajani said:
1 decade ago
I have tried putting y as 5 in both the equation but it is not giving x as 60. Please explain.
Rakesh said:
1 decade ago
Do we any alternative method for this because this method is time consuming.
Satish said:
1 decade ago
(200/x)+(400/y) = 8+(20/60).
=> 200(1/x+2/y) = 25/3.
=> 1/x+2/y = 25/(3*200).
By cancellation we get,
1/x+2/y = 1/24.
=> 200(1/x+2/y) = 25/3.
=> 1/x+2/y = 25/(3*200).
By cancellation we get,
1/x+2/y = 1/24.
Sukanya said:
1 decade ago
Convert 20 minutes into hrs, 20/60 = 1/3 hrs.
Since it s 20 minutes more than the 8 hrs,
Total time = (1/3)+8 = 25/3 hrs.
Since it s 20 minutes more than the 8 hrs,
Total time = (1/3)+8 = 25/3 hrs.
Srijan said:
1 decade ago
How it comes 25/3 please explain?
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