"Life is like riding a bicycle. To keep your balance you must keep moving."
- Albert Einstein
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:
[A].
2 : 3
[B].
3 : 2
[C].
3 : 4
[D].
4 : 3
Answer: Option B
Explanation:
Let the speed of the train be x km/hr and that of the car be y km/hr.
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:
(Thu, Aug 12, 2010 06:14:07 AM)
Its not 8*(20/60). Its 8+(20/60) that gives us 25/3.
Das said:
(Sun, Aug 22, 2010 09:48:58 AM)
Hi could you tel me how this 1/15 came in Step 1 ?
Shwetha said:
(Mon, Sep 6, 2010 02:51:00 PM)
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:
(Tue, Sep 28, 2010 03:33:05 AM)
Please tell me how did you get the X value?
Deepu said:
(Sun, Oct 3, 2010 06:45:02 AM)
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.
Hari said:
(Thu, Mar 3, 2011 01:49:09 PM)
Is there any short method for this?
Mathi said:
(Wed, Mar 30, 2011 02:19:41 PM)
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
Sandy said:
(Mon, May 2, 2011 07:08:44 AM)
Please can any one tell me how did you get the 8 in first step?
Mani said:
(Wed, Jun 1, 2011 04:29:09 PM)
Please can any one tell me how did you get the 1/24 in first step?
Manasa said:
(Tue, Jun 14, 2011 01:54:49 AM)
Please can any one help out this problem.
How they got 8 in first step?
Kavitha said:
(Fri, Jun 17, 2011 06:12:05 AM)
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
Kishore said:
(Sat, Aug 6, 2011 01:19:05 PM)
Hello sir, how did come 1/15 at 1st step ?
Rajeshwari said:
(Sun, Sep 25, 2011 06:50:56 PM)
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
Ratio of speeds = 60 : 80 = 3 : 4.