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 1 of 9.
Vids said:
2 decades ago
Hi, from wher that 25/3 came?
(2)
Anu said:
2 decades ago
Hey as it takes 20mins more for car to travel 200km... then time becomes 8hrs20mins.... so by converting dis time totally into hrs... 8*(20/60)...dis fraction brings u 25/3.
Hrushikesh said:
2 decades ago
Its not 8*(20/60). Its 8+(20/60) that gives us 25/3.
(1)
Das said:
1 decade ago
Hi could you tel me how this 1/15 came in Step 1 ?
Shwetha said:
1 decade ago
Hi das 120 (1/x+4/y) = 8 then 1/x+4/y=8/20 that is equal to 1/x+4/y=1/15.
Bharatesh said:
1 decade ago
Please tell me how did you get the X value?
Deepu said:
1 decade ago
By doing eqn(1) - eqn(2) we can get:
(4/y)-(2/y) = (1/15)-(1/24)
(4y-2y)/y2=(8-5)/120
2y/y2=3/120
2/y=1/40
y=80
By placing y value in eqn(1) we get x = 60.
(4/y)-(2/y) = (1/15)-(1/24)
(4y-2y)/y2=(8-5)/120
2y/y2=3/120
2/y=1/40
y=80
By placing y value in eqn(1) we get x = 60.
Hari said:
1 decade ago
Is there any short method for this?
(1)
Mathi said:
1 decade ago
Here to solve short cut method....
1/x+4/y=1/15 --> take xy as multiples
(y+4x)/xy=1/15 --> take 15 to left hand side
15y + 60x=xy
Similarly
1/x+2/y=1/24
24y+48x=xy
now easy to equate
15y+60x=24y+48x
60x-48x=24y-15y
12x=9y
x/y=9/12 --> x/y=3/4
hence 3:4
1/x+4/y=1/15 --> take xy as multiples
(y+4x)/xy=1/15 --> take 15 to left hand side
15y + 60x=xy
Similarly
1/x+2/y=1/24
24y+48x=xy
now easy to equate
15y+60x=24y+48x
60x-48x=24y-15y
12x=9y
x/y=9/12 --> x/y=3/4
hence 3:4
(1)
Sandy said:
1 decade ago
Please can any one tell me how did you get the 8 in first step?
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