grater than 2 and smaller than 400

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sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members; Location: India; Thanked: 267 times; GMAT Score:760

by sanju09 » Sat Jun 19, 2010 2:05 am

For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32

The mind is everything. What you think you become. -Lord Buddha

Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
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Source: Beat The GMAT — Problem Solving | Sat Jun 19, 2010 2:05 am

kvcpk: Legendary Member; Posts: 1893; Joined: Sun May 30, 2010 11:48 pmFollowed by: 7 members; Thanked: 215 times

by kvcpk » Sat Jun 19, 2010 2:22 am

sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32

For any integer value of n, n^2 is positive..
So, 2 n^2 + 1 is always greater than 2. except for n= 0

2n^2 +1 <400
2n^2 <399
n^2<199
so n should be less than or equal to 14 or greater than or equal to -14 [14^2 = 196]

so total possible values for n should be 28 [excuding 0]

D

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amising6: Master | Next Rank: 500 Posts; Posts: 294; Joined: Wed May 05, 2010 4:01 am; Location: india; Thanked: 57 times

by amising6 » Sat Jun 19, 2010 2:47 am

sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32

2 n^2 + 1<400
2n^2<399
n^2<199 (approx)
now all the number whose square less than 199
14 ^2 =196
and it will have to be greate than 2
so answer will include all the number between 1 and 14 so 14
so answer A

Ideation without execution is delusion

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sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members; Location: India; Thanked: 267 times; GMAT Score:760

by sanju09 » Sat Jun 19, 2010 2:54 am

amising6 wrote:
sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32
2 n^2 + 1<400
2n^2<399
n^2<199 (approx)
now all the number whose square less than 199
14 ^2 =196
and it will have to be greate than 2
so answer will include all the number between 1 and 14 so 14
so answer A

For integer n and 2 n^2 + 1 > 2, n cannot take 0; hence, on the number line, all integers from -14 to 14 EXCEPT 0 fulfill the need. Is it still A, man?

The mind is everything. What you think you become. -Lord Buddha

Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

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amising6: Master | Next Rank: 500 Posts; Posts: 294; Joined: Wed May 05, 2010 4:01 am; Location: india; Thanked: 57 times

by amising6 » Sat Jun 19, 2010 2:57 am

sanju09 wrote:
amising6 wrote:
sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32
2 n^2 + 1<400
2n^2<399
n^2<199 (approx)
now all the number whose square less than 199
14 ^2 =196
and it will have to be greate than 2
so answer will include all the number between 1 and 14 so 14
so answer A
For integer n and 2 n^2 + 1 > 2, n cannot take 0; hence, on the number line, all integers from -14 to 14 EXCEPT 0 fulfill the need. Is it still A, man?

no dude my case was only for positve integer
if you include negative integr it will be 28

thanks

Ideation without execution is delusion

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