Bret discovers 150 bags of his favorite cookies contain a total of 3750 cookies. He the discovers that the cookies in a bag are normally distributed with a standard deviation of 5 . When Bret goes to buy a bag of his favorite cookies, how many of the 1200 bags in the store contain more than 30 cookies?
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cookie crazy bret
Source: Beat The GMAT — Problem Solving |
Actually, you can solve this, but it definitely won't show up on the GMAT.
You first find the average number of cookies in each bag:
3750 cookies / 150 bags = 25 cookies per bag
We know the standard deviation is 5. We want to find the amount of cookies out of 1200 bags at the store that have more than 30 cookies.
If you remember what a normal distribution curve looks like, you know that about 15.8% exceed one standard deviation. 15.8% of 1200 is 189.6, so my guess is 189 bags.
This will not show up on the GMAT b/c the GMAT does not expect you to know the fractions that fall into each standard deviation range.
You first find the average number of cookies in each bag:
3750 cookies / 150 bags = 25 cookies per bag
We know the standard deviation is 5. We want to find the amount of cookies out of 1200 bags at the store that have more than 30 cookies.
If you remember what a normal distribution curve looks like, you know that about 15.8% exceed one standard deviation. 15.8% of 1200 is 189.6, so my guess is 189 bags.
This will not show up on the GMAT b/c the GMAT does not expect you to know the fractions that fall into each standard deviation range.
I know it is. I found a similar problem in my PR guide that expected me to know the percent breakdowns of each standard deviation range in a normal distribution. You don't have to know that on the real thing. None of my practice problems from the official guide nor my GMATPrep and Powerprep exams ever expected me to know that.
