gmat prep Q5
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 88
- Joined: Fri Nov 16, 2007 2:05 am
-
- Senior | Next Rank: 100 Posts
- Posts: 91
- Joined: Mon Dec 31, 2007 4:54 pm
- Location: Houston
- Thanked: 1 times
Ok, I tried answering this... But, somehow I don't get the correct answer. This problem looks pretty straight.. But, I am still not getting the OA.
(squareroot of 2+ squareroot of 5)^2, I tried using (a+b)^2= a^2+2ab+b^2... By that, I get 2+2(2)(5)+5=17. The OA is 13. Hmm.. Interesting..
May be Stuart can help on this...
(squareroot of 2+ squareroot of 5)^2, I tried using (a+b)^2= a^2+2ab+b^2... By that, I get 2+2(2)(5)+5=17. The OA is 13. Hmm.. Interesting..
May be Stuart can help on this...
- Stuart@KaplanGMAT
- GMAT Instructor
- Posts: 3225
- Joined: Tue Jan 08, 2008 2:40 pm
- Location: Toronto
- Thanked: 1710 times
- Followed by:614 members
- GMAT Score:800
Your substitution is wrong.smar83 wrote:Ok, I tried answering this... But, somehow I don't get the correct answer. This problem looks pretty straight.. But, I am still not getting the OA.
(squareroot of 2+ squareroot of 5)^2, I tried using (a+b)^2= a^2+2ab+b^2... By that, I get 2+2(2)(5)+5=17. The OA is 13. Hmm.. Interesting..
May be Stuart can help on this...
The middle term is 2ab. In this case, a=root2 and b=root5. You've substituted a=2 and b=5.
You should have gotten:
2 + 2(root2)(root5) + 5 = 7 + 2(root10) = 7 + 2(approx3) = approximately 13
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
-
- Senior | Next Rank: 100 Posts
- Posts: 88
- Joined: Fri Nov 16, 2007 2:05 am
Sid
actually I found it. it's simple.
(sqrt 2 + sqrt5)^2=
2+2.^2^5+5=
7+2^10=
approxim 13 (2^10=6 approxim)
cheers
Nad
actually I found it. it's simple.
(sqrt 2 + sqrt5)^2=
2+2.^2^5+5=
7+2^10=
approxim 13 (2^10=6 approxim)
cheers
Nad