Help with Word Problem (Compass Test)

Steve can make 4 drinks per min (20/5). Sue can make 2 drinks per min (20/10). Jack can make 1.33 drinks per minute (20/15). Add 4+2+1.33 = 7.33 drinks per minute all together. 20 drinks / 7.33 drinks per minute = 2.72 min = 2 min 43.7 sec.

Eta: thanks for making my day...quite proud I can still do this.....As a mom I don't feel like I have a brain most days ;). But I do have a engineering degree so it would be sad if I couldnt figure it out, lol!

I like the way Stephanie explained it. I was looking at it as a "Work Problem." The formula I teach my students looks a little weird at first, but it will apply to problems that are not as easy to do the way she explained it.

(Time Together/Time Alone #1) + (Time Together/Time Alone #2) + ... = 1

The "1" stands for "1 whole job," meaning one lawn or one project or, in this case, one set of "20 drinks." So, in your example it would be:

x/5 + x/10 + x/15 = 1
The least common denominator is 30, so multiply everything by 30:

30x/5 + 30x/10 + 30x/15 = 30*1
6x + 3x + 2x = 30
11x = 30
x = 2.727272 ...
x = 2 min 44 sec.

I hope that helped. I'm so much better explaining these things in person than on the computer :-) Math is one of the most difficult subjects to jump back into, so hang in there and good luck!

I'm not sure, but it seems reasonable to me for you to begin by figuring out how many drinks each bartender made per minute. This is, of course, assuming that the three of them worked with amazing consistency and didn't taste any of their own product.

Glad you've rec'd help. For future reference, there is a most excellent website called Khan Academy that is free .Take a look!