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 2 of 9.
Mani said:
1 decade ago
Please can any one tell me how did you get the 1/24 in first step?
Manasa said:
1 decade ago
Please can any one help out this problem.
How they got 8 in first step?
How they got 8 in first step?
Kavitha said:
1 decade ago
Hi manasa,
let the speed of the train be x kmph
let the speed of the car be y kmph
it is given that 120km is done by train,so D=120
by the formula D=S*T
T=120/X
and also given the rest is done by the car,
so D=600-120=480 km
T=480/y
then,120/x+480/y=8(read the question given problem clearly,in pbm it is given that to complete 600km journey,it will take 8hrs).
==>1/x+4/y=1/15...............eq1
similarly in case 2:
time for
train=200/x
car=400/y
and also given in pbm 20 min more so,
200/x+400/y=25/3(8hrs+20min=25/3)
==>1/x+2/y=1/24...............eq2
for solving these two equations as mathi said
then u will get 3:4
Hope u understand.
Bye
let the speed of the train be x kmph
let the speed of the car be y kmph
it is given that 120km is done by train,so D=120
by the formula D=S*T
T=120/X
and also given the rest is done by the car,
so D=600-120=480 km
T=480/y
then,120/x+480/y=8(read the question given problem clearly,in pbm it is given that to complete 600km journey,it will take 8hrs).
==>1/x+4/y=1/15...............eq1
similarly in case 2:
time for
train=200/x
car=400/y
and also given in pbm 20 min more so,
200/x+400/y=25/3(8hrs+20min=25/3)
==>1/x+2/y=1/24...............eq2
for solving these two equations as mathi said
then u will get 3:4
Hope u understand.
Bye
Kishore said:
1 decade ago
Hello sir, how did come 1/15 at 1st step ?
Rajeshwari said:
1 decade ago
Hi kishore,
The first eqn is
(120/x)+(480/y)=8
120[(1/x)+(4/y)]=8
(1/x)+(4/y)=8/120
(1/x)+(4/y)=1/15
similarly in the second eqn
(200/x)+(400/y)=25/3
200[(1/x)+(2/y)]=25/3
(1/x)+(2/y)=25/(3*200)
(1/x)+(2/y)=1/24
The first eqn is
(120/x)+(480/y)=8
120[(1/x)+(4/y)]=8
(1/x)+(4/y)=8/120
(1/x)+(4/y)=1/15
similarly in the second eqn
(200/x)+(400/y)=25/3
200[(1/x)+(2/y)]=25/3
(1/x)+(2/y)=25/(3*200)
(1/x)+(2/y)=1/24
(1)
Kamal said:
1 decade ago
Please explain how 1/15 and 1/24 comes ?
Sagar said:
1 decade ago
Hi @kamal,
To solve the equation 1 and 2 easily we had taken 120, 200 common from equations.
To solve the equation 1 and 2 easily we had taken 120, 200 common from equations.
Prasad said:
1 decade ago
Train speed = 80/20*60 = 240km.
Car speed = 600-240 = 360km.
Ratio 240:360 or 3:4.
Car speed = 600-240 = 360km.
Ratio 240:360 or 3:4.
(1)
Darshan Kumar said:
1 decade ago
Hi , Any one can tell me in detail how 25/3 came ?
Ravichandran.k said:
1 decade ago
@Darshan kumar,
That car take more 20 min so 8.20 mins.
8+20/60= 8+1/3 = 8*3+1=24/3 is come.
That car take more 20 min so 8.20 mins.
8+20/60= 8+1/3 = 8*3+1=24/3 is come.
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