SOLUTION: David and Moira are trying to bake a chocolate cake for Alexis’ birthday. They require 300g of chocolate that is 86% cocoa. Johnny has two types of chocolate: one that is 80% co

Question 1175937: David and Moira are trying to bake a chocolate cake for Alexis’ birthday. They require 300g of
chocolate that is 86% cocoa. Johnny has two types of chocolate: one that is 80% cocoa and
another that is 90% cocoa. What is the quantity of each type of chocolate that David and Moira
need to use to make Alexis’ birthday cake?
Answer by ikleyn(52855) (Show Source): You can put this solution on YOUR website!
.


Let x = amount (the mass in grams) of the 90% cocoa.

Then the mass of the 80% cocoa is  (300-x) grams.


After that, write the standard equation of conservation mass (the pure cocoa)

in the mixture before and after the mixing


    0.9x + 0.8(300-x) = 0.86*300.


From this equation


    x =  = 180.


ANSWER.  180 grams of the 90% cocoa and the rest, (300-180) = 120 grams of the 80% cocoa.


CHECK.  I will check the concentration   = 0.86 = 86%.    ! Precisely correct !

Solved.

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In this site, there is entire bunch of lessons covering various types of mixture problems.

Of them the most closest to your problem are
    - Word problems on mixtures for dry substances like coffee beans, nuts, cashew and peanuts
    - Word problems on mixtures for dry substances like candies, dried fruits
    - Word problems on mixtures for dry substances like soil and sand

Read them and become an expert in solution the mixture word problems.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Mixture problems".

Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.

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