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- divya.1024
- Course Students
- Posts: 19
- Joined: Wed Aug 07, 2013 10:08 am
Word Problems: Chapter 10, #20 (pg 173) - Stuck!
Can anyone please explain on how to solve this problem. I assumed this can be taken as normal distribution, I am afraid it doesn't work that way!
- tommywallach
- Manhattan Prep Staff
- Posts: 1917
- Joined: Thu Mar 31, 2011 11:18 am
Re: stuck with prob 20 ( chapter 10 - page 173)
Hey Divya,
So don't apply standard deviation stuff unless the question says the words "normal distribution" or "standard deviation." This is a weighted average question, which has nothing to do with SD.
In this case, we know that we have more than twice as many 20-lb. boxes as 10-lb boxes. Think of it this way, if we had EXACTLY twice as many 20-lb boxes, then that would mean we have exactly FOUR times as much weight in the 20-lb boxes (because the pomegranates inside each box weigh twice as much, and there are twice as many of the boxes). So our ratio would be 1:4, in terms of weight of 10lb pomegranates:weight of 20lb pomegranates.
In percentage terms, that would be 20%:80%.
But we know we have MORE than twice as many 20-lb boxes. So we can't have 20% and 80% (that's EXACTLY twice as many). The only possible answer is 15%. If 15% of the weight is 10-lb pomegranates, then the other 85% could be 20-lb pomegranates. (That would represent MORE than twice as many boxes of pomegranates that weight twice as much.)
-t
So don't apply standard deviation stuff unless the question says the words "normal distribution" or "standard deviation." This is a weighted average question, which has nothing to do with SD.
In this case, we know that we have more than twice as many 20-lb. boxes as 10-lb boxes. Think of it this way, if we had EXACTLY twice as many 20-lb boxes, then that would mean we have exactly FOUR times as much weight in the 20-lb boxes (because the pomegranates inside each box weigh twice as much, and there are twice as many of the boxes). So our ratio would be 1:4, in terms of weight of 10lb pomegranates:weight of 20lb pomegranates.
In percentage terms, that would be 20%:80%.
But we know we have MORE than twice as many 20-lb boxes. So we can't have 20% and 80% (that's EXACTLY twice as many). The only possible answer is 15%. If 15% of the weight is 10-lb pomegranates, then the other 85% could be 20-lb pomegranates. (That would represent MORE than twice as many boxes of pomegranates that weight twice as much.)
-t
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