Quant Basics for Zeros in Quant - CAT 2012

If Rakesh and Ramesh take 10 days and 12 days respectively to complete a job they work on alternate days to complete it with rakesh starting the job,find the time in which the job would have been completed(in days)
ans is 65/6(10 5/6).....thanks

A precious stone worth Rs 10872 fell and broke into three pieces, the weights of which are proportional to 1:2:3. The value of each stone is directly proportional to the square of its weight. Find the loss in the value caused by the breakage.

a) 3624
b) 4228
c) 6644
d) 7510

Kindly post the steps to solve as well. Thank you in advance


Sol :- Here given that the weights of broken pieces are in ratio 1:2:3.
k,2k,3k are the weights. So we add them and get the total weight.
k+2k+3k = 6k
Let us assume that the constant be 1. (v proportional W^2 => v = xw^2)
here we assume x to be 1. then
(6k)^2 = 36k^2 = 10872
k^2 = 10872/36
Broken pieces = k^2 + (2k)^2 + (3k)^2 = 14k^2
Value that got reduced = 36k^2 - 14k^2 = 22k^2
Substitute the value of K^2
22* 10872/36 = 6644
Option C
ajayjr Says
Hi Shashank Can u plz explain how u arrived at the boldened part?


10 women can do work in 7 days, 10 children can do it in 14 days. Work will be same.
10w*7 = 10c*14
70 w = 140 c
w = 2c
So he substituted 2c in place of w. 😃
If Rakesh and Ramesh take 10 days and 12 days respectively to complete a job they work on alternate days to complete it with rakesh starting the job,find the time in which the job would have been completed(in days)
ans is 65/6(10 5/6).....thanks


Sol : Rakesh does the work in a day = 1/10
Similarly ramesh = 1/12.
In 2 days work completed = 1/10 + 1/12 = 11/60
The work is completed when it is 60/60 = 1
In 10 days it will become 55/60 ( Since in 2 days it is 11/60 )

Now work left = 5/60 = 1/12
Now its rakeshs turn as he started the work. 1/10 > 1/12. So it wont take a complete day.
1/10 *x = 1/12
x = 10/12 = 5/6th of a day.
Therefore total work is completed in 10 5/6 days = 65/6. 😃

at
HydRocker
bro can u explain me that frm where we are getting 10 days and how it is becoming 55/60 plze tell in detail i will be very thankfull to u

at
HydRocker
bro can u explain me that frm where we are getting 10 days and how it is becoming 55/60 plze tell in detail i will be very thankfull to u http://www.pagalguy.net/pagalguy/smilies/icon_confused.gif

at
HydRocker
bro can u explain me that frm where we are getting 10 days and how it is becoming 55/60 plze tell in detail i will be very thankfull to u


See first thing is 1/10 and 1/12 are the works done in a day.
Now rakesh will start work and then the other person and that continues
1/10+1/12+1/10+1/12+............

So what i did is i calculated work done for 2 days which is 1/10+1/12 = 11/60
Now we should make it 60/60. But it is not possible last possible fraction less than 60/60 is 55/60. How we got it 5* 11/60.
Since 11/60 is work done in 2 days. we have multiplied it with 5 , so we get work done in 10 days which is 55/60. Now 5/60 work is left which is less than 1/10. so we know that i wont take exact 1 day but it will take less than a day to complete it. so i did 1/10 * x = 1/12
x = 10/12 = 5/6th day the work gets completed totally. so it is 10 5/6 days.

Hope it is clear now... 😃

thanks bro for doing this ...hey i am new to this thread and i recently joined time and i am quite weak in quant so can u tell me that how i can begin my preparation to become strong in this section .....any tips frm ur side...

thanks

thanks bro for doing this ...hey i am new to this thread and i recently joined time and i am quite weak in quant so can u tell me that how i can begin my preparation to become strong in this section .....any tips frm ur side...

thanks


Do whatever you want but just do basics. Don't go for high level questions straight away. Do basics, build your concepts by end of june and then give mocks and analyse. But basics are very very important. Without basics nothing can be done.... 😃
HydRocker Says
Do whatever you want but just do basics. Don't go for high level questions straight away. Do basics, build your concepts by end of june and then give mocks and analyse. But basics are very very important. Without basics nothing can be done.... :)


like i am having times material so i will start from their material like i have seen it include some difficult questions too as they are having a mixture of questions topics of varying difficulty so what to do in that case either to continue or follow some other books

subscribing


1. 1/30+1/40-1/25 = > 55 min

2. 16*12 (1/24*16+1/32*24) =>3/4
1/4 work to be done

2(16+x/24*16+16/32*24) = 1/4
x=24 days

3. 6*2/12*4.........total work done 1/4......3/4 work to be done

3/4 = 3*x/15*4
x=15

4. 1/A+ 2/A+4/A = 1/5
A =35



in 4 th question can u explain me that how you are getting the value of c as c is 2b which is 2(2a)=4a and u have written 4/a in place of c instead of 1/4a?

HYDROCKER - u doing a fantastic job ! That same problem i posted in the quants thread and three kind fellas solved it but i cudnt understand the steps...

Let us assume that the constant be 1. (v proportional W^2 => v = xw^2)
here we assume x to be 1. then
what exactly is X here and can u also explain what is the meaning of PROPORTIONALITY CONSTANT?

HYDROCKER - u doing a fantastic job ! That same problem i posted in the quants thread and three kind fellas solved it but i cudnt understand the steps...

Let us assume that the constant be 1. (v proportional W^2 => v = xw^2)
here we assume x to be 1. then
what exactly is X here and can u also explain what is the meaning of PROPORTIONALITY CONSTANT?


See x here is proportionality constant. Proportionality can be of two kinds direct and indirect.
One quantity A is said to vary directly as another quantity B if the two quantities depend upon each other in such a manner that if B is increased in a certain ratio, A also increases in the same ratio and same thing when the ratio decreases. Then we say A directly proportional to be.
So we get A/B = x (constant) or the ratio of two quantities is a constant.
How much ever A increases the same amount is increased in B so the ratio always tend to be same (Constant).

P and Q are filling pipes which can fill a tank in 15 min and 20 min. R is emptying pipe which can empty a full tank in 30 minutes.the three pipes are operated continuously one after the other in order of p,q,r each being kept opened for 2 minutes untill the tank is filled.after how much time will tank be full?

A 30 minutes
B 32 2/3 min
C 36 min
D 34 min

P and Q are filling pipes which can fill a tank in 15 min and 20 min. R is emptying pipe which can empty a full tank in 30 minutes.the three pipes are operated continuously one after the other in order of p,q,r each being kept opened for 2 minutes untill the tank is filled.after how much time will tank be full?

A 30 minutes
B 32 2/3 min
C 36 min
D 34 min


Sol :- P = 1/15
Q = 1/20
R = - 1/30 ( Because it is emptying )
Now for 2 minutes if they are opened they can fill or empty 2/15,2/20, -2/30 respectively. So for 1st 6 minutes the tank is filled = 2/15+2/20-2/30 = 1/6.
So 1/6th tank is filled in 6 minutes. Now in 5*6 = 30 minutes 5/6th tank will be filled. 1/6 is left. P can fill 2/15 in 2 minutes.
so 5/6+2/15 = 29/30 . So 1/30th part is remaining to be filled. But Q fills 1/20 part in 1 minute. ( 1/20>1/30)
So 1/20*x = 1/30
x = 2/3 ( In 2/3 min the tank becomes full )
so total time taken = 30+2+2/3 = 32 2/3 minutes.
Option B
P and Q are filling pipes which can fill a tank in 15 min and 20 min. R is emptying pipe which can empty a full tank in 30 minutes.the three pipes are operated continuously one after the other in order of p,q,r each being kept opened for 2 minutes untill the tank is filled.after how much time will tank be full?

A 30 minutes
B 32 2/3 min
C 36 min
D 34 min

Here, let the Tank is filled by 60 units of water(LCM of 15,20 and 30). Then, every minute, Pipe P fills 4 units of water, Pipe Q fills 3 units and Pipe R takes out 2 units. Then every six minutes, since each pipe is being used for 2 minutes, 8+6-4 units i.e 10 units are being filled. So after 6*5 minutes, i.e. 30 minutes, the tank is filled 50 units.
Next 2 minutes, it will be filled an extra 8 units. The next minute it will be filled 3 units, but we need only 2 units (60-5. So it will take 32 and 2/3 minutes!!
So the answer is 32/3 minutes bhai!!

Hope you get it!! Do let me know if something is missing!!

Guys this is a simple problems i came across recently.....very simple stuff but i just didnt understand the final step. can anyone of u be kind enuff to explain the boldened bit.

1)The ratio of the monthly incomes of A and B is 4:3. The ratio of their monthly expenditure is 5:4. if A saves one fourth of his monthly income, find the ratio of their monthly savings.

Sol - let Incomes be A = 4x, B = 3x
let monthly expenditures be A = 5y, B = 4y
Monthly savings of A = (4x - 5y)
Monthly savings of B = (3x - 4y)
Given that 4x - 5y = 1/4(4x)
=> 3x = 5y

Therefore Monthly savings of B = 3x - 4y = 5y - 4y
i.e = y

required ratio = 1/4(4x):y = x : y = 5:3
(( How did they arrive at x:y = 5:3))

Guys this is a simple problems i came across recently.....very simple stuff but i just didnt understand the final step. can anyone of u be kind enuff to explain the boldened bit.

1)The ratio of the monthly incomes of A and B is 4:3. The ratio of their monthly expenditure is 5:4. if A saves one fourth of his monthly income, find the ratio of their monthly savings.

Sol - let Incomes be A = 4x, B = 3x
let monthly expenditures be A = 5y, B = 4y
Monthly savings of A = (4x - 5y)
Monthly savings of B = (3x - 4y)
Given that 4x - 5y = 1/4(4x)
=> 3x = 5y

Therefore Monthly savings of B = 3x - 4y = 5y - 4y
i.e = y

required ratio = 1/4(4x):y = x : y = 5:3
(( How did they arrive at x:y = 5:3))






now 3x = 5y
so x/y = 5/3

which means x:y = 5:3
Yaar these Quant pros solve the problem but dont post explanations...someone plz solve and post explanation!
After the addition of 35 liters of water to a can of diluted milk, the concentration of milk in the can becomes 30%. Now, further 40 liters of water is added to the can and the concentration of milk in the
can gets reduced by 10 percentage points. How many more liters of water must be added to the can now such that the concentration of milk in the can becomes 8%?
(a) 160 (b) 180 (c) 175 (d) 200