Page 1 of 1 [ 7 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: Weighted Average P. 91Posted: Thu Oct 20, 2011 10:37 am

Joined: Wed Oct 19, 2011 10:20 am
Posts: 4
Hello,

I was hoping you could help me solve the problem on page 119 in book 10 using the number-line strategy.

I understand that Brand Q is closer to 15 than Brand P. However beyond that step-I'm lost.

Thanks

Top

 Post subject: Re: Weighted Average P. 91Posted: Thu Oct 20, 2011 4:14 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
Here is the correct approach:

P = amount of brand P
Q = amount of brand Q

64 = P + Q ... total amount of mix

15 = .20P + .25Q ... amount of almonds in the mix

64 = P + Q
15 = .20P + .25Q

64 = P + Q
1500 = 20P + 25Q

1280 = 20P + 20Q
1500 = 20P + 25Q

- 220 = -5Q

Q = 220/5 = 44

- Veritas Help

Top

 Post subject: Re: Weighted Average P. 91Posted: Thu Oct 20, 2011 4:37 pm

Joined: Wed Oct 19, 2011 10:20 am
Posts: 4
Thank you, however the response did not answer my question.

I am interested in using the number-line strategy that is highlighted earlier in the book. Again I understand that brand Q is closer to 15 than Brand P. Its the following steps that I am unsure of.

Top

 Post subject: Re: Weighted Average P. 91Posted: Thu Oct 20, 2011 4:44 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
if we had all P: 64 * .2 = 12.8

If we had all Q: 64 * .25 = 16

Since 15 is closer to 16 than it is to 12.8, the mixture must have more Brand Q than Brand P, so that rules out choices A, B, and C

if we try choice E, we get: 16*.2 + 48 * .25 = 3.2 + 2 = 15.2, so the correct answer must be D

Top

 Post subject: Re: Weighted Average P. 91Posted: Thu Oct 20, 2011 5:46 pm

Joined: Wed Oct 19, 2011 10:20 am
Posts: 4
My apologies, I will be more specific with my questions.

I understand that Brand Q is closer to 15.

My question corresponds to the next step after we discover that Brand Q is closer to 15. Why does this information (Brand Q being closer to 15) mean that choices A, B, C are ruled out. Additionally where does the 48 come from? Is the number-line strategy mainly used for questions that require ratio answers?

Also I think that 3.2 + 12= 15.2 The pre-written response for this problem contains an error, as it shows only 2 and not 12. You may want to update this in the pre-written answers that are sent out in response to email and forum questions.

Top

 Post subject: Re: Weighted Average P. 91Posted: Fri Oct 21, 2011 1:08 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
The number line strategy is much more useful when we don't have something with 64 potential steps spread over a range of only 5 percentage points...
I.e. - if we had 64 percentage points - where one was 20% nuts and the other was 84% nuts, then we'd be more able to apply the number line strategy here --
As it is, we have 5 percentage points.
If we had equal amounts of P and Q, (32 oz each) then we'd have 22.5% nuts in the final mix. Since we have 15/64 of the final mix almonds, which is roughly 23%. This means we must have more of the mix that contains 25% almonds than the mix that has 20% almonds.

Here's the concept:
The higher the proportion of the 25% mix we have, the higher the proportion of almonds in the final mix, and at the extreme end, if we have 100% of Brand Q, then we have 25% almonds in the final mixture. If, on the other hand, we have 100% of Brand P, then we have 20% almonds in the final mixture. Since our final mix is about 23%, we know that this is skewed closer to 25% than to 20%, telling us we have slightly more of Brand Q than of Brand P.

Hope this helps a bit -
Apologies for the typo - we don't use pre-written answers on these, so occasionally we make a typo in our calculations. We do our best to catch these, but one slips through from time to time. Hopefully, it doesn't detract from the explanation itself or the concepts presented.

Veritas Help

Top

 Post subject: Re: Weighted Average P. 91Posted: Mon Oct 24, 2011 8:05 am

Joined: Wed Oct 19, 2011 10:20 am
Posts: 4
Great! Thanks for the explanation!

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 7 posts ]

 All times are UTC - 8 hours [ DST ]

#### Who is online

Users browsing this forum: No registered users and 1 guest

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

 Search for: