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Sub 505 (Easy)|   Statistics and Sets Problems|   Word Problems|                     
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Bunuel
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There must be something easy that i just don't get for me :
8*12(3/8) = 36 as you simplify the 8 between them. Therefore how do you manage to arrive at 99?

I guess it must be something different of spelling or something?

Thanks a lot for your help !
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Gmbrox
There must be something easy that i just don't get for me :
8*12(3/8) = 36 as you simplify the 8 between them. Therefore how do you manage to arrive at 99?

I guess it must be something different of spelling or something?

Thanks a lot for your help !

It's not 12 multiplied by 3/8. it's \(12\frac{3}{8}=\frac{12*8+3}{8}=\frac{99}{8}\) (the same way as \(1\frac{1}{2}=\frac{3}{2}\)).
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I used ratio of packages, which is 2:1.
converted both to the same fractions, so
15 1/4 = 15 2/8

2x(12 3/8) + 1x( 15 2/8) = 24+15+ 6/8+2/8 = 39 and 8/8, 8/8 is also obviously 1. Could also be together 40 but that's not easily divisible with three and you know you're left with a remainder. Instead just:
39/3 + 1/3 = 13 and 1/3
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Total weight on Monday \(= 8*12 + 8 * \frac{3}{8} = 96 + 3\)

Total weight on Tuesday \(= 4*15 + 4 * \frac{1}{4} = 60 + 1\)

Average of all days \(= \frac{96 + 60 + 4}{12} = 8 + 5 + \frac{4}{12} = 13\frac{1}{3}\)

Answer = A
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Bunuel
SOLUTION

On Monday, a person mailed 8 packages weighing an average (arithmetic mean) of \(12\frac{3}{8}\) pounds, and on Tuesday, 4 packages weighing an average of \(15\frac{1}{4}\) pounds. What was the average weight, in pounds, of all the packages the person mailed on both days?

(A) \(13\frac{1}{3}\)

(B) \(13\frac{13}{16}\)

(C) \(15\frac{1}{2}\)

(D) \(15\frac{15}{16}\)

(E) \(16\frac{1}{2}\)

Solution:

To solve this question we can use the weighted average equation.

Weighted Average = (Sum of Weighted Terms) / (Total Number of Items)

We'll first determine the sum (numerator). We see that on the first day we had 8 items that averaged 12 3/8 pounds. We don't know the weights of the individual packages, but we can determine that the sum of all 8 packages is:

Sum of first day's packages = 8 x 12 3/8 = 99 pounds

Similarly, the sum of the second day's packages is:

Sum of second day's packages = 4 x 15 ¼ = 61

We now can use the weighted average equation to find the average weight of the 12 packages:

Weighted Average = (99 + 61) / 12

Weighted Average = 160 /12

Weighted Average = 13 1/3

Answer: A
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letsamf
I know this question without this fraction and I’m complete lost WHERE this fraction come frommm?
On Monday, a person mailed 8 packages weighing an average (arithmetic mean) of pounds, and on Tuesday, 4 packages weighing an average of pounds. What was the average weight, in pounds, of all the packages the person mailed on both days?

(A) 13 1/3

(B) 13 13/16

(C) 15 1/2

(D) 15 15/16

(E) 16 1/2

I could find the result of entire number but I still don’t get where this fraction come from!
I have to use the weighted average calculation right?

Posted from my mobile device

Hey,

You need to know the common fractions in and out. Haven’t found the original post but pls see attached a picture from my notes. A lot of question will translate easy when you know the fractions and their decimal equivalent and reversely as well.
Attachments

4D1A0A49-DC08-4EFE-8ABD-AA1797E92D1F.jpeg
4D1A0A49-DC08-4EFE-8ABD-AA1797E92D1F.jpeg [ 2.45 MiB | Viewed 21882 times ]

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Quote:
On Monday, a person mailed 8 packages weighing an average (arithmetic mean) of \(12\frac{3}{8}\) pounds, and on Tuesday, 4 packages weighing an average of \(15\frac{1}{4}\) pounds. What was the average weight, in pounds, of all the packages the person mailed on both days?

(A) \(13\frac{1}{3}\)

(B) \(13\frac{13}{16}\)

(C) \(15\frac{1}{2}\)

(D) \(15\frac{15}{16}\)

(E) \(16\frac{1}{2}\)
We're going to make weighted average of \(12\frac{3}{8}\) (with 8 packages) and \(15\frac{1}{4}\) (4 packages). So, the correct answer must be between these two numbers. Choice C,D, and E are beyond of these two numbers, so they are out.
We're going to make the weighted average, but choice B is simply the ''regular'' average (\(12\frac{3}{8}\) + \(15\frac{1}{4}\))/2= \(13\frac{13}{16}\), which indicates choice B. So, B is out. Correct choice is A.
Hope it helps.
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Bunuel
On Monday, a person mailed 8 packages weighing an average (arithmetic mean) of \(12\frac{3}{8}\) pounds, and on Tuesday, 4 packages weighing an average of \(15\frac{1}{4}\) pounds. What was the average weight, in pounds, of all the packages the person mailed on both days?

(A) \(13\frac{1}{3}\)

(B) \(13\frac{13}{16}\)

(C) \(15\frac{1}{2}\)

(D) \(15\frac{15}{16}\)

(E) \(16\frac{1}{2}\)





Nick Slavkovich, GMAT/GRE tutor with 20+ years of experience

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