Topscore Math Problem

[americanpierg]

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how many ounces of pure apple pulp must be added to 30 ounces of a 20% solution of apple pulp to make it a 50% solution

A. 18
B. 22
C. 13
D. 47
E. 44

which is the right answer and how did u get that answer please.

 

[hausee]

(30*20%+x*100%)/(30+x)=50%
"solute"/total=percentage.

x=18

 

[americanpierg]

(30*20%+x*100%)/(30+x)=50%
"solute"/total=percentage.

x=18

thanks, make sense now. for some reason i was thinkning of cross multiplying like with molarities.