Word problem. Need equation and solution

Question

A recipe calls for 2 1/3 cups of flour to make  3 1/2 dozen cookies.  How many cups of flour are needed to make 5 dozen cookies?

Answer 1

Dear Heather,

    You can do this by writing down a proportion.

 

cups of flour/dozen of cookies    =   cups of flour/dozen of cookies   Here is the pattern.

 

 

2 1/3 cu of flour/ 3 1/2 dozen of cookies      =      X  unknown cu. of flour/ 5 dozen cookies

 

Cross multiply

 

3 1/2  X   = 5 (2 1/3)       Change the mixed numbers into improper.

 

7/2 X = 5 ( 7/3)               Solve for "X."   Multiply both sides of equation by reciprocal of 7/2, which is 2/7

 

(2/7 (7/2)X  = 5 (7/3)(2/7)          X= 10/3  =____________Just divide 10 by 3.   You should get a whole number

 

and a fraction (mixed number)                                                  Cups of flour

 

If you have any further questions, just ask me.  If you like my work, please give me a thumbs up.

 

                                                  Susan C.