You are preparing mashed potatoes for Thanksgivings and the recipe calls for 6 ounces of cream cheese to be added to 1lb of mashed potatoes. What is the percent concentration of cream cheese in the final preparation (w/w)?

Question

My answer:
6 oz (30 gm/1 oz) = 180 gm
1 lb = 454 gm

(180 gm/454 gm) = (x/100 gm)

x = 39.6%

Answer 1

your technique is good

there are 16 ounces in a pound
... 6 / 16 = 3 / 8 = .375

converting to metric seems to have affected the accuracy

Answer 2

Well, two problems:
First
when you ask for the percentage of the result, that means of the sum.
180 g + 454 g = 634 g result
so we need
100 *180/634 = 28.4 %
Second
If they give you creepy old crude units they probably want you to use them
1 lb = 16 oz
so we have
6 oz + 16 oz = 22 oz
100 * 6/22 = 27.3 %

Answer 3

You have me worried now because there is some fundamental stuff going on here.
This is a percentage by MASS problem. In classical science mass does not disappear. Therefore if you mix two things by mass the percnt of one of them in the final will be the percent of the SUM of the two original masses.
There is another kind of very similar but very different problem.
What if you put a cubic centimeter of salt into 100 cubic centimeters of water?
then the volume would not change and the percent of salt by volume would be 100 * 1/100 = 1% BY VOLUME
however the percent by mass would be 100 (mass of salt)/(mass of salt +mass of water)

Answer 4

Sticking with the medieval units ....

total mixture = 16 + 6 or 22 oz
percentage of cream = 6/22*100% = 27.3 %