Official Quant thread for CAT 2013

pyashraj · February 20, 2013, 10:20am

@nam2aspire

Shld be 1/4th I guess..

Given, In a period of 90 days, No. of Service hour required = 5/6

Hence, In a period of 1 day, No. of Service hour required = 5/540

Similarly, Post Overhauling, In a period of 120 days, No. of Service hr required = 5/6

Hence, In a period of 1 day, No. of Service hour required = 5/720

Hence, Fraction of Service hour saved = (5/540 - 5/720)/(5/540)

=>540*1/(180*12) = 1/4..

nyancat · February 20, 2013, 10:53am

@nam2aspire said:
hello all,
please explain me this question and its solution.

A motorcycle,before overhauling,requires 5/6 hour service time every 90 days, while after overhauling, it requires 5/6 hour service time every 120 days. what fraction of the pre-overhauling service time is saved in the latter case?

I am not getting what is being asked in this question?

please help

thanks in advance

120 days------ 5/6

so in 90 days-3/4*5/6=15/24=5/8

so saved..5/6-5/8=5/24

so fraction saved

5/24/5/6=1/4?????????

manjulneogi · February 20, 2013, 10:53am

N=202*20002*200000002*200....2(15 ZEROES)*200000....2(31 zeroes).
The sum of the digits in this multiplication will be X.
Then X=?

ilovetorres · February 20, 2013, 11:10am

@MANJULNEOGI said:
N=202*20002*200000002*200....2(15 ZEROES)*200000....2(31 zeroes). The sum of the digits in this multiplication will be X. Then X=?

7?

nyancat · February 20, 2013, 11:12am

@MANJULNEOGI said:
N=202*20002*200000002*200....2(15 ZEROES)*200000....2(31 zeroes).
The sum of the digits in this multiplication will be X.
Then X=?

32 32 times..

so

5*32=160??

saurav205 · February 20, 2013, 11:20am

@MANJULNEOGI said:
N=202*20002*200000002*200....2(15 ZEROES)*200000....2(31 zeroes). The sum of the digits in this multiplication will be X. Then X=?

Divide by 9...

oa 2 hai kya???

rkshtsurana · February 20, 2013, 11:22am

@MANJULNEOGI said:
N=202*20002*200000002*200....2(15 ZEROES)*200000....2(31 zeroes). The sum of the digits in this multiplication will be X. Then X=?

4*4*4*4*4 ( i am assuming there are nly five terms.. bcz no of zeros in between is of form 2^n - 1 )
4^5 mod 9
4^3 = 1 mod 9
4^5 = 16 mod 9
remainder 7
so sum of digits 7 or 16 or of form 9n+7..have to depend on options

scrabbler · February 20, 2013, 11:28am

@iLoveTorres said:
7?

Sum of digits is not the same as digital sum. Digital sum is what you get by dividing by 9 and taking remainder ("casting out the nines").

For example, the digital sum of 345 is 3 while the sum of digits is 12.

regards
scrabbler

mohitjain · February 20, 2013, 11:32am

1)A solid sphere is cut into 16 identical pieces with 5 cuts. What is the percentage increase in the combined total surface area of all the pieces over that of the original sphere?

ilovetorres · February 20, 2013, 11:34am

@scrabbler said:
Sum of digits is not the same as digital sum. Digital sum is what you get by dividing by 9 and taking remainder ("casting out the nines").For example, the digital sum of 345 is 3 while the sum of digits is 12.regardsscrabbler

so how should you approach these questions?
And considering that in your example sum of the digits is 12 i.e divisior+digital sum. can i generalise this and conclude for the above question that the digit sum is 9+7=16? or does this depend on the number of times the number is divided by 9. which in your example was once so k=1 but in the above mentioned question it is 6 times so 9(6)+7=61?

rkshtsurana · February 20, 2013, 11:34am

@scrabbler said:
Sum of digits is not the same as digital sum. Digital sum is what you get by dividing by 9 and taking remainder ("casting out the nines").For example, the digital sum of 345 is 3 while the sum of digits is 12.regardsscrabbler

exactly it ll be of form 9n+7..but wat of all four options of of this form nly

scrabbler · February 20, 2013, 11:35am

@mohitjain said:
A solid sphere is cut into 16 identical pieces with 5 cuts. What is the percentage increase in the combined total surface area of all the pieces over that of the original sphere?

250%?

regards
scrabbler

scrabbler · February 20, 2013, 11:37am

@iLoveTorres said:
so how should you approach these questions?And considering that in your example sum of the digits is 12 i.e divisior+digital sum. can i generalise this and conclude for the above question that the digit sum is 9+7=16?

No it could be 7 or 16 or 25 or any 7 + 9n

The original question I will see if I can type out an explanation 😞 Thoda lamba hai and am very busy at work at the moment (for a change)...shayad raat ko...

regards
scrabbler

mohitjain · February 20, 2013, 11:39am

2)A, B, C are the vertices of a triangle of area 60 cm2. Let AD be the median from A on BC and BY be the median from B on AD. If BY is extended to meet AC in E, what is the area of triangle AYE?

ilovetorres · February 20, 2013, 11:40am

@mohitjain said:
2)A, B, C are the vertices of a triangle of area 60 cm2. Let AD be the median from A on BC and BY be the median from B on AD. If BY is extended to meet AC in E, what is the area of triangle AYE?

15?

mohitjain · February 20, 2013, 11:43am

@iLoveTorres said:
15?

no ..its nt d correct OA..if we extend BY to meet AC in E den BE is nt median...wic wud giv 15 as d OA..

nam2aspire · February 20, 2013, 11:45am

@Logrhythm said:
in 90 days -> 5/6 hrs=> in 1 day -> 5/(6*90) = 1/108 hrs a day...in 120 days -> 5/6 hrs=> in 1 day -> 5/(6*120) = 1/144 hrsfraction saved -> 1/108-1/144 = (4-3)/432 = 1/432 hrs/day is saved??

this is wrong

ilovetorres · February 20, 2013, 11:46am

@mohitjain said:
no ..its nt d correct OA..if we extend BY to meet AC in E den BE is nt median...wic wud giv 15 as d OA..

so is it 10?

scrabbler · February 20, 2013, 11:47am

@mohitjain said:
2)A, B, C are the vertices of a triangle of area 60 cm2. Let AD be the median from A on BC and BY be the median from B on AD. If BY is extended to meet AC in E, what is the area of triangle AYE?

10?

regards
scrabbler

mohitjain · February 20, 2013, 11:47am

@iLoveTorres said:
so is it 10?

no its nt 10!