Pls help with Power-Prep algebra question

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 170
Joined: Mon Oct 22, 2007 4:36 am
Thanked: 7 times

Pls help with Power-Prep algebra question

by erjamit » Sun Aug 03, 2008 5:24 am
Pls help with the attached Power-Prep algebra question

OA is C
Attachments
PowerPrep2 Algebra.jpg
Last edited by erjamit on Sun Aug 03, 2008 5:50 am, edited 1 time in total.

Junior | Next Rank: 30 Posts
Posts: 12
Joined: Fri Mar 28, 2008 10:07 am

by prees20 » Sun Aug 03, 2008 5:35 am
is the answer II only?

Master | Next Rank: 500 Posts
Posts: 170
Joined: Mon Oct 22, 2007 4:36 am
Thanked: 7 times

by erjamit » Sun Aug 03, 2008 5:50 am
yes OA Is C

Junior | Next Rank: 30 Posts
Posts: 12
Joined: Fri Mar 28, 2008 10:07 am

by prees20 » Sun Aug 03, 2008 6:15 am
When in doubt- plug in numbers. The question says x and y are positive. I could have plugged in fractions but I used integers to make it easier on me. You should use a positive fraction after if you dont get an answer. I am not sure if this is the eight way to do it, but this is how I usually solve these kind of questions.

I just plugged in x = 2 and y = 2

1/ (x + y)^ (1/2) = 1/2

so you need to plus in value for x and y and see which of the given choices are greater than 1/2

1) (4) ^ (1/2) / 4 = 1/2 is equal to the equation therefore not right
2) (2)^1/2 + (2)^(1/2) / 4 = 2 * 2^(1/2) / 4 = (1/2) * (2)^(1/2) , which is > 1/2
3) 0 / 4 = 0 not greater than 1/2

Note - x^(1/2) is same as x *sqrt 2

Hence C is your answer


Let me know if you have questions.