Some QR questions(Please help).

[sam12]

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[FONT=arial,helvetica]If Sam can do a job in 4 days that Lisa can do in 6 days and Tom can do in 2 days, how long would the job take if Sam, Lisa, and Tom worked together to complete it?

.[FONT=arial,helvetica]If Steven can mix 20 drinks in 5 minutes, Sue can mix 20 drinks in 10 minutes, and Jack can mix 20 drinks in 15 minutes, how much time will it take all 3 of them working together to mix the 20 drinks?.

 

[sicspeed]

I'm not positive if this is correct, but this is how I would do it...
Sam and Lisa first
4x6/(4+6)= 2.4
then Tom
2.4x2/(2.4+2)= 1.09 Days

Similar for the next problem

 

[Danny289]

[FONT=arial,helvetica]If Sam can do a job in 4 days that Lisa can do in 6 days and Tom can do in 2 days, how long would the job take if Sam, Lisa, and Tom worked together to complete it?

.[FONT=arial,helvetica]If Steven can mix 20 drinks in 5 minutes, Sue can mix 20 drinks in 10 minutes, and Jack can mix 20 drinks in 15 minutes, how much time will it take all 3 of them working together to mix the 20 drinks?.

Hi Sam
there are formula for these questions;
(1/4) +(1/6) +(1/2)=(1/X)
now find the X =======> X= 12/11 X= 1.09

 

[sam12]

Thanks so much guys. Both of those ways are helpful.

 

[sam12]

I have another question as well.

Jill has 6 different books. In how many ways can she select 2 different books?

I initially thought that to solve this problem you have to do (6x5)/(2x1), which would give 15, but its wrong and its a permutation problem of 6x5= 30, which is the right answer. How can I differentiate between permutation and the way I was trying to do it initially(I think its called combination?)

 

[Streetwolf]

I have another question as well.

Jill has 6 different books. In how many ways can she select 2 different books?

I initially thought that to solve this problem you have to do (6x5)/(2x1), which would give 15, but its wrong and its a permutation problem of 6x5= 30, which is the right answer. How can I differentiate between permutation and the way I was trying to do it initially(I think its called combination?)

It's a very poorly worded problem. My initial reaction would be to use a combination as well, since who cares in what order she chooses the books.

I'm sure you won't get something like this on the DAT.

 

[sam12]

It's a very poorly worded problem. My initial reaction would be to use a combination as well, since who cares in what order she chooses the books.

I'm sure you won't get something like this on the DAT.

Its actually a problem posted on the exam that is on the ADA site itself, so I feel a bit concerned lol. But yeah its confusing. I just want to know how to differentiate between the two.

Off topic, streetwolf, I see that you got into Stony Brook, thats amazing, Congrats. Any tips lol? How did you do on the DAT and where did you do undergrad from?

 

[Streetwolf]

Its actually a problem posted on the exam that is on the ADA site itself, so I feel a bit concerned lol. But yeah its confusing. I just want to know how to differentiate between the two.

Off topic, streetwolf, I see that you got into Stony Brook, thats amazing, Congrats. Any tips lol? How did you do on the DAT and where did you do undergrad from?

http://www.predents.com/?page=user&user_id=1563

Any tips for QR? Just do practice problems. I was a math major in undergrad so I never had to study for it. But I would definitely look over an ass-load of problems, especially in areas you don't know that well.