Help: GMAT Prep 9 Math Questions

lauyeung · Last edited by lauyeung on Sun Apr 20, 2008 12:22 pm; edited 1 time in total

Please help with these 9 math questions! I know this will probably be very easy for you guys, but I'm stuck. Sad

Please provide explanations as to why they are the correct answers...thanks!

lauyeung · Posted: Sun Apr 20, 2008 12:21 pm Post subject:

Questions 4-6

lauyeung · Posted: Sun Apr 20, 2008 12:22 pm Post subject:

questions 7 - 9

lauyeung · Posted: Sun Apr 20, 2008 3:54 pm Post subject:

Someone please help! I'm taking my GMAT in two days!!

nishuonly · Posted: Mon Apr 21, 2008 11:49 am Post subject:

1. avg speed = total dist / total time;
2. put a and b in function and add them. then put (a+b) in function and see if sum matches.
3. no idea
4. 4c2 * 3c2
5. 24 = (2/3) * pi*D where D is diameter
6. no idea
7. 1/10 ..couldnt get any other solution.
8. no idea.
9. same as 1.

hope these tips help you.

lauyeung · Posted: Mon Apr 21, 2008 1:59 pm Post subject:

JoJo_618 · Posted: Tue Apr 22, 2008 9:00 am Post subject:

I'm Chinese, so I don't know if I can explain it clearly.
2. ∵f(a)=2/a, f(b)=2/b,
∴f(a)+f(b)=2/a+2/b=2(a+b)/ab;
but f(a+b)=2/(a+b);
if a=2,b=4, then 2(a+b)/ab=3/2; 2/(a+b)=1/3; so D is wrong.
3. If we know both of them, then ∠RQS=∠RSQ, ∠TSU=∠TUS.
∵∠P=90 ∴ ∠R+∠T=90
and∵∠R=180-2∠RSQ ∠T=180-2∠TSU.
∴∠R+∠T=(180-2∠RSQ)+(180-2∠TSU)=90
∴ ∠RSQ+∠TSU=135, so ∠X=180-135=45.
Hope u can understand these~~ Smile

gabriel · Posted: Fri Apr 25, 2008 10:33 am Post subject:

@lauyeung .. the reason you are not getting enough responses is because you have posted 9 questions on a single thread. Open separate threads for each of them and believe me you will get an excellent response. You are also breaking board rules by posting more than one question on a thread. Please do post these questions in separate threads in the appropriate section i.e. Problem Solving and Data Sufficiency. I am locking this thread.

Regards

PS:- Welcome to Beat the GMAT Very Happy