The Official CAT 2007 Quant Thread

[blacof]

5x - (5/12)9 + 9 / 12x = 9/16

5x - 15/4 + 9 /12x= 9/16


108 x = 80x - 60 + 144


28x = 84 => x =3 therefore initial quantity of a =21 litres and b is 15 litres

[blacof]

bhai log kya ho raha hai ... cmon post some qs guys

[gauravbrills]

Hi can anybdy help me in this Q'n not entirely sure of the ans ..

Two men are walking towards each other alongside a railway track. A freight train overtakes one of them in
20 seconds and exactly 10 minutes later meets the other man coming from the opposite direction. The train
passes this man in 18 seconds. Assume the velocities are constant throughout.

1 How long after the train has passed the second man will the two men meet?
(A) 89.7 minutes (B) 90 minutes
(C) 90.3 minutes (D) cannot be determined from above

2 The ratio of the velocities of the first man to the second man is
(A) -10: 9 (B) 9:10
(C) -9: 10 (D) undeterminable from above

and this

Q Laila drives to the station each day to pick up her husband Majnu, who usually arrives on a train
o’clock. Last Monday, Majnu finished work earlier, caught an earlier train and arrived at the station
5 o’clock. He started to walk home and eventually met Laila who drove him the rest of the
getting home 20 minutes earlier than usual. On Tuesday, he again finished early and found himself
the station at 5:30. Again he began to walk home, again he met Laila on the way, and she drove
home the rest of the way. Assume constant speed throughout with no wasted time for waiting,
of the car etc. How much earlier than the usual time were they home on Tuesday?
(A) 6 minutes (B) 8 minutes (C) 10 minutes (D) 12 minutes

Cheers

[blacof]

20 = L / T - A time taken to cross A

18 = L / T + B Time taken to cross B

(T -A ) * 20 = ( T + B ) * 18

T -A / T + B = 9/10

10 T - 10A = 9T + 9B

T = 10 A + 9B

(D - L) / T =600 Time taken to meet B where D is the distance between them

D = 600 T + L

substituting for T and L

6000A + 5400 B + 200A + 180 B -20A = 6180A + 5580 B


Time required for both to meet is given
[D - 618 (A + B )] /A+B = D/A+B -618

20 [ ( 30A )/A+B + 1 ) - 618

Not able get past this

[blacof]

Originally Posted by gauravbrills

Hi can anybdy help me in this Q'n not entirely sure of the ans ..

Two men are walking towards each other alongside a railway track. A freight train overtakes one of them in
20 seconds and exactly 10 minutes later meets the other man coming from the opposite direction. The train
passes this man in 18 seconds. Assume the velocities are constant throughout.

1 How long after the train has passed the second man will the two men meet?
(A) 89.7 minutes (B) 90 minutes
(C) 90.3 minutes (D) cannot be determined from above

2 The ratio of the velocities of the first man to the second man is
(A) -10: 9 (B) 9:10
(C) -9: 10 (D) undeterminable from above

and this

Q Laila drives to the station each day to pick up her husband Majnu, who usually arrives on a train
o’clock. Last Monday, Majnu finished work earlier, caught an earlier train and arrived at the station
5 o’clock. He started to walk home and eventually met Laila who drove him the rest of the
getting home 20 minutes earlier than usual. On Tuesday, he again finished early and found himself
the station at 5:30. Again he began to walk home, again he met Laila on the way, and she drove
home the rest of the way. Assume constant speed throughout with no wasted time for waiting,
of the car etc. How much earlier than the usual time were they home on Tuesday?
(A) 6 minutes (B) 8 minutes (C) 10 minutes (D) 12 minutes

Cheers

for the second Q the first part is not clear ..

[STALWART]

Originally Posted by gauravbrills

Hi can anybdy help me in this Q'n not entirely sure of the ans ..

Two men are walking towards each other alongside a railway track. A freight train overtakes one of them in
20 seconds and exactly 10 minutes later meets the other man coming from the opposite direction. The train
passes this man in 18 seconds. Assume the velocities are constant throughout.

1 How long after the train has passed the second man will the two men meet?
(A) 89.7 minutes (B) 90 minutes
(C) 90.3 minutes (D) cannot be determined from above

2 The ratio of the velocities of the first man to the second man is
(A) -10: 9 (B) 9:10
(C) -9: 10 (D) undeterminable from above

and this

Q Laila drives to the station each day to pick up her husband Majnu, who usually arrives on a train
o’clock. Last Monday, Majnu finished work earlier, caught an earlier train and arrived at the station
5 o’clock. He started to walk home and eventually met Laila who drove him the rest of the
getting home 20 minutes earlier than usual. On Tuesday, he again finished early and found himself
the station at 5:30. Again he began to walk home, again he met Laila on the way, and she drove
home the rest of the way. Assume constant speed throughout with no wasted time for waiting,
of the car etc. How much earlier than the usual time were they home on Tuesday?
(A) 6 minutes (B) 8 minutes (C) 10 minutes (D) 12 minutes

Cheers

Hi

1) For the first one the answer is 92.7 minutes though its not given in the options . Came in JMET recently !! If we disregard the 18 and 20 seconds while computing the answer's later part then the answer will be 90 minutes . But thats wrong for sure !!

2) For the second one .. Ratio cant be determined !!

3) For the third one Assume .. say Laila starts at 4:00 and reaches at 5:00 at station then proceed . The ratio of speeds will come out to be ( 5: 1 :: Car : Majnu )
Answer is 10 minutes !!

... Sayonara

[blacof]

HEy stalwart can you post the approach for the above 2 problems

[sidcool007]

can anyone help me on this

possible remainders of...
7^n/12...
7^n/35
6^n/10

well some of them can be solved by putting in the values and getting remainders...but i need the concept to find it

[blacof]

Well there many techniques that u can use depending on the value of n

7^n /12 = 7 ^ (n%4) /12

7 ^ n /35 => number is of the form 7k and need to find remainder when

7 ^n/5 => 2^n/5

6 ^ n /10 = > this is always 6 since any power of 6 ends in 6

[bdebbarma]

Originally Posted by sidcool007

can anyone help me on this

possible remainders of...
7^n/12...
7^n/35
6^n/10

well some of them can be solved by putting in the values and getting remainders...but i need the concept to find it

try reading this post on all the concepts regarding finding remainders in Number Theory

http://www.pagalguy.com/forum/564125-post1858.html