If a+b = 12, and 1/a + 1/b= 6, then what should be the value of ab
(A) 1/2
(B) -3
(C) 2
(D) -2
(E) 1/6
I have seen this problem on www.TC.com/GRE, in sample questions. kindly solve it by an another method
Looking for a good reply.
Target Test Prep is 20% off right now!
Use code FLASH20
Available with Beat the GMAT members only code
MORE DETAILS
kindly solve it by giving explanation.......
This topic has expert replies
-
testcircle
- Newbie | Next Rank: 10 Posts
- Posts: 1
- Joined: Sun Dec 27, 2009 9:52 pm
-
heshamelaziry
- Legendary Member
- Posts: 869
- Joined: Wed Aug 26, 2009 3:49 pm
- Location: California
- Thanked: 13 times
- Followed by:3 members
-
thephoenix
- Legendary Member
- Posts: 1560
- Joined: Tue Nov 17, 2009 2:38 am
- Thanked: 137 times
- Followed by:5 members
Look,
1/a + 1/b = (a+b)/2
(b+a)/ab = (a+b)/2
simply, ab = 2
if i talk about my opinion then according to me you should to visit to that particular site where from you found this question, because i have also seen these type problem on https://www.TestCircle.com/GMAT FREE SAMPLE VIDEOS, and i found that it was described in a simple and understanding way.
1/a + 1/b = (a+b)/2
(b+a)/ab = (a+b)/2
simply, ab = 2
if i talk about my opinion then according to me you should to visit to that particular site where from you found this question, because i have also seen these type problem on https://www.TestCircle.com/GMAT FREE SAMPLE VIDEOS, and i found that it was described in a simple and understanding way.
-
reply2spg
- Legendary Member
- Posts: 1261
- Joined: Sun Sep 14, 2008 3:46 am
- Thanked: 27 times
- GMAT Score:570
Answer is C. however, this question should be in quant section.
ok here is the solution.
(1/a) +(1/b) = 6
Find out the LCM of both fractions. it is 'ab'. multiply by 'b' to first term and by 'a' to second term. final result will be
[(a+b)/ab] = 6.
We know that a+b =12. replace a+b with 12 in the equation.
[12/ab] = 6. Move 'ab' to right hand side and '6' to left hand side.
(12/6) = ab. Therefore, ab = 2 (C)
ok here is the solution.
(1/a) +(1/b) = 6
Find out the LCM of both fractions. it is 'ab'. multiply by 'b' to first term and by 'a' to second term. final result will be
[(a+b)/ab] = 6.
We know that a+b =12. replace a+b with 12 in the equation.
[12/ab] = 6. Move 'ab' to right hand side and '6' to left hand side.
(12/6) = ab. Therefore, ab = 2 (C)
[/b]testcircle wrote:If a+b = 12, and 1/a + 1/b= 6, then what should be the value of ab
(A) 1/2
(B) -3
(C) 2
(D) -2
(E) 1/6
I have seen this problem on www.TC.com/GRE, in sample questions. kindly solve it by an another method
Looking for a good reply.
