GRE® math problems

[Ofayyaz]

Can you please put me wise, with quick (GRE like) approach:

1. A pencil box contains 2 red, 4 white and 5 black balls. In how many ways can 4 balls be drawn from the box if at least one white ball is to be included in the draw?

2. Bruce would take 16 hrs more to complete the job individually, than working together with Berry. If Berry worked alone, she would take 9 hrs more to complete the job than Bruce and Berry who worked together. In how much time would both working together complete the job?

Thanks

[Supper]

1. Since you always have at least 1 white ball for every draw, you will have 10 balls left in the box. Now all you need to do is choose 3 more balls out of 10. We're gonna use Combination formula since the order of the balls is not important. The number of ways 4 balls can be drawn is: 10C3 = 10!/(10-3)!3! = 120 ways

2. Let x be the hours it took Bruce and Berry to complete the job together, so Bruce would take (x +16) hrs and Berry would take (x +9) hrs to complete the job individually.
---Together in 1hr they would have done 1/(x +16) + 1/(x+9) = [(x+16)+(x+9)] / [(x+16)(x+9)] = (2x+25)/(x^2+25x+144) of the job
Now you can form a proportion: 1hr together they could do >>>>>>>>>>>(2x+25)/(x^2+25x+144) of the job
======================== x hrs together they could do >>>>>>>>>>1 whole job

Now cross multiply you have: x(2x+25)/(x^2+25x+144) = 1 <=> 2x^2 + 25x = x^2 +25x + 144
Solve the equation you have: x = 12 hrs

[Ofayyaz]

Thank you so much.

I took GRE on 11 Feb. I scored 800 q 750 v 5 AWA. :)

[Nachikey]

hi, Ofayyaz,
Could you give me some tips for preparing for the verbal section on GRE. Ive learned over 2100 words . Is that enough?
Thanks.

[Kwame1983]

Hello friends,

I really need help preparing for the GRE. I took the test twice but performed poorly. The first time I had 340 on the Verbal, 380 on quantitative and 3.5 on the analytical writing. The second attempt I scored 340 on verbal, 400 on quantitative, and 3.5 on the analytical. Obviously there was no significant improvement in my scores.

I don't want to give up as if GRE is not doable. I have seen people testify about high scores and believe I can hit the highest score. I really need to get into a graduate program in Public Administration and need to score 1200 or better. I really need friends to advice me about various strategies that proved helpful.

Counting on your advice