Official Quant thread for CAT 2013

@IIM-A2013 said:
The total expenses of a boarding house is partly fixed and partly varying linearly with the number of boarders.the average expense per boarder is rs 700 when there are 25 boarders and rs 600 when there are 50 boarders, what is the average expense per boarder when there are 100 boarders?a.550b.580c.540d.570please suggest.
F - Fixed
V - Variable

17500 = 25V + F
30000 = 30V + F

Solving we get
V = 500, F = 5000

SO for 100 boarders, 55000/100 = 550
If x 2, then which of the following is true for all real values of x and y?

a) x + 2y b) 3y + 2x > 0
c) 2x – xy >0
d) 2x – xy > 1
How to solve this kinda, without assuming values? Please post approach.
@Torque024 said:
If x 2, then which of the following is true for all real values of x and y?a) x + 2y 0 c) 2x – xy d) 2x – xy > 1 How to solve this kinda, without assuming values? Please post approach.
option C ?
@Torque024 said:
If x 2, then which of the following is true for all real values of x and y?a) x + 2y 0 c) 2x – xy d) 2x – xy > 1 How to solve this kinda, without assuming values? Please post approach.
bhai Check ur c option......plz clarify it
@Torque024 said:
If x 2, then which of the following is true for all real values of x and y?a) x + 2y 0 c) 2x – xy d) 2x – xy > 1 How to solve this kinda, without assuming values? Please post approach.
option C 2x-xy>0 he hoga. logic kuch anhi h values check karke he answer nikalte h
@19rsb said:
bhai Check ur c option......plz clarify it
Yeah, edited.
@Torque024 said:
If x 2, then which of the following is true for all real values of x and y?a) x + 2y 0 c) 2x – xy d) 2x – xy > 1 How to solve this kinda, without assuming values? Please post approach.
a) x + 2y one can convert the equations into lines and then regions

b) would a line passing though center ....
d) rectangular hyperbola ..

well you can plot and see roughly to get to the answer.
still the i would try min and max value before proceeding to graphs
@AIM_IIM_2013 said:
option C 2x-xy>0 he hoga. logic kuch anhi h values check karke he answer nikalte h
har cheej ka logic hota hai, values put krke to aa hi jayega
@Torque024 bhai logic istemal karna is nt useful in this type of question :P
@Torque024 ye he best approach h. graph wali approach aur time consuming aur complicated hogi.
@AIM_IIM_2013 said:
@Torque024 ye he best approach h. graph wali approach aur time consuming aur complicated hogi.
@sauravd2001
Yeah, I know. It's an easy question. But the main thing is approach, values put karna would be a kinda hit and trail. So was searching ki koi logic ho.
There is a spring kept vertically fixed at one end with a ball attached to its other end.It is compressed to 60 cm from its mean position before releasing.Due to certain energy losses,every time the compression reduces by a factor of 0.75.Find the total distance traveled by the ball attached to the spring in cm.
Assume for a spring (compression from mean position= expansion from mean position)
@Torque024 i think..option c ..becse..2x-xy>0..so...
x(2-y) >0...in this condition ,,
we hv x will be always -ve becse..x
i.e. 2-y2...fianly only thsi condiont satisfied the above given condition ..according
the rule of neccessary and sufficeint condition ...c is only answer....
@Harmeet89 said:
I am unnecessarily getting confused for this question"How many numbers from 1 to 700 are multiples of 2 or 3 but not 7 ?"I know that some common multiples of 2 and 3 may have to be subtracted because they appear twice in the addition. Also the number of multiples of 7 will have to be subtracted from the total number but somehow I am getting confused
350 + 233 -116-(50 + 33 -16)=400?
@19rsb hmm 400 hi aa raha hai mera bhi aur tere wale ka kya answere hai bhai?
@19rsb said:
There is a spring kept vertically fixed at one end with a ball attached to its other end.It is compressed to 60 cm from its mean position before releasing.Due to certain energy losses,every time the compression reduces by a factor of 0.75.Find the total distance traveled by the ball attached to the spring in cm.Assume for a spring (compression from mean position= expansion from mean position)
120(1+3/4+3^2/4^2....)
=480 cm
@Harmeet89 700 mein se 350 multiples honge 2 ke
aur 233 honge 3 ke but 3 ke multiples conincide karenge 2 walon ke sath n adhe 3 ke coincide karenge toh 116 gaye ismeinse
bache 466 aur 7 ke 100 multiple honge aur ismein se 50 coincide karenge 2 walon ke sath toh bache 416 aur 3 ke sath 33 coincide karenge lekin 3 wale 2 ke sath jo adhe honge toh 16 gaye bache 400
@Harmeet89 said:
I am unnecessarily getting confused for this question"How many numbers from 1 to 700 are multiples of 2 or 3 but not 7 ?"I know that some common multiples of 2 and 3 may have to be subtracted because they appear twice in the addition. Also the number of multiples of 7 will have to be subtracted from the total number but somehow I am getting confused
multiples of 2 - 700/2 = 350
multiples of 3 - 700/3 = 233
multiples of 2 and 3 - 700/6 = 116
multiples of 2 and 7 - 700/14 = 50
multiples of 3 and 7 - 700/21 = 33
multiples of 2,3 and 7 - 700/42 = 16

350+233-116-(50+33-16) = 400
@Harmeet89 are dekh 3 wale jo 7 ke multiples honge woh honge 21,42,63 thik hai ?
693=21+(n-1)21
n=33
ab 33/2=16 kyunki 42,84 2 ke bhi toh multiple honge
@krum said:
120(1+3/4+3^2/4^2....)=480 cm
bhai I dont hav d OA ......but I am getting 900 for this .......r u missing anything here ....or I may be wrong.......ur take(explanation).......