[Ankurb]

Originally Posted by kumarbe

total number of terms from s{1} to s{15} = 1 + 2+3+ 4...+15=120so s{15} will be {106,107,....120}so sum of all numbers in s{15} would be 63 * 15 = 945
Ankurb ..Plz correct me if and where i am wrong..

your logic is ok. Plz check the bold part. It should be

113 * 15 = 1695

[abhay15783]

Originally Posted by Aloha

17^17^17 /15
-> 2^17^17 /15
-> 2^289 /15
-> (16^72 * 2 ) /15
rem = 2

M I wrong anywhere ?

Your answer is correct but 17^17 does not equal to 289
you took it as 17^2

kindly check your approach to avoid mistakes in other questions (U got lucky with this answer though )

[vineet.nitd]

Originally Posted by kumarbe

total number of terms from s{1} to s{15} = 1 + 2+3+ 4...+15=120so s{15} will be {106,107,....120}so sum of all numbers in s{15} would be 63 * 15 = 945Ankurb ..Plz correct me if and where i am wrong..

You are actually commiting mistake in taking avg of 106 and 120, which will be 113 instead of 63.

Sum {S(n)} = n[2summation (n)-n+1]/2
=>Sum {S(15)} = 15*(2*15*8-14)/2= 15*113=1695

[Aloha]

Originally Posted by abhay15783

Scores can vary from 40 to -10

But 51 scores are not possible scores you can get
actually i did this with quite a tedious approach

Wanted an easier solution and that's why posted this over here

Oh by the way the answer is 45

Which are the scores that we can't get?

[abhay15783]

Originally Posted by Aloha

Which are the scores that we can't get?

you cant get 39 for example
Try it out you will find a lot more

[simrat_sandy]

if (a^m+b^m)/2 > (a+b/2)^m
a and b are positive unequal real numbers then m cannot be
-2
-1/2
2
1/2

[ragra.1017]

Originally Posted by libi

Hello, Please clear my doubts on these questions.
Q1.In how many ways can 10 soldiers stand in 2 rows having 5 soldiers in each row?

a.7257600
b.235600
c.923500
d.35400

Q2. There are 4 different letters and 4 addressed envelopes. In how many ways can the letters be put in the envelopes so that atleast one letter goes to the correct address??
a.15
b.16
c,18
d.12

Q3. In above find the number of ways in which none of the letters go to the correct address?

a.6
b.9
c.10
d.11

Will post reply tommorrow

I know this was posted ages back, but the first question has bothered me since then. Most of the people felt that the answer to the first should have been 10! but we then didn't consider the possibility that the soldiers can face toward or back of each other! Thus, the answer should be 10!*2. Correct me if I'm wrong!

Richa.

[kumarbe]

Originally Posted by kumarbe

There was a data sufficency problem in the recent AIMCAT regarding expressing a number as the difference of two squares...anyone plz elucidate the conditions for the sameThe solution said "If a number is divisble by 2 and not by 4 it cannot be wriiten as the difference of two squares.."Can someone prove this...

Guys ,plx throw some light on this ..

[shashank3012]

Originally Posted by kumarbe

Guys ,plx throw some light on this ..

If a number is divisble by 2 and not by 4 it cannot be wriiten as the difference of two squares.

either the numbers are odd or even both so that the difference is a multiple of 2.

so,case 1:both even.

(2a)^2-(2b)^2=4a^2-4b^2=4k

case 2:both odd

(2a+1)^2-(2b-1)^2

4a^2+4a+1-4b^2+4b-1

again 4k.

so,it should be divisible by 4 always,if it is divisible by 2

hope that helps.

[hi.shivani]

Originally Posted by ragra.1017

I know this was posted ages back, but the first question has bothered me since then. Most of the people felt that the answer to the first should have been 10! but we then didn't consider the possibility that the soldiers can face toward or back of each other! Thus, the answer should be 10!*2. Correct me if I'm wrong!

Richa.

Hey Richa,
Do we ever consider like this..??
Many a times the question is like this chair arrange in a row or two row do we ever consider the orientation of the chair or so..??
We have even questions like people standing in two rows for taking photographs et al. We dont consider the direction of the people's faces..Don't you think then we have to consider so many directions from 0-360( it will be infinite)..!!