I need 2 3/4 cups of flour to make 48 cookies, how much flour will i need to make 120 cookies?

Question

I need 2 3/4 cups of flour to make 48 cookies, how much flour will i need to make 120 cookies?

 

Answer 1

This is a proportion problem. You should setup the proportion like this:

 

 

2.75 cups flour                              X

________________        =    ________________

48 Cookies                                    120 Cookies

 

You will then use the cross products rule (or butterfly rule as I like to call it) to setup an equation to solve for X

 

 

The cross product rule is you multiply one fraction's denominator with the other fraction's numerator. So we can choose to multiply 2.75 times 120 (typed in orange) and get 330. Then you multiply the first fractions numerator with the other fraction's denominator, so in this case 48 times X (typed in green) and you get 48X

 

Now you are left with the equation 48X = 330.

Now you just have to isolate the X by dividing both sides by 48.

X = 6.875 or 6 7/8 cups of flour.

 

Hope this helps!!!

Jesse L.

Answer 2

Hello Jenny, 

You can do this problems many different ways, but I will do it by setting up proportions

 

First, I am going to convert 2 3/4 into a decimal.  That will be 2.75.

Now, this is the proportion that I will use, and again there are 4 ways you can set up proportions.

 

(2.75 cups of flour)/ 48 cookies. = ( x cups of flour)/ 128 cookies

 

Using cross products, I get 

 

 (2.75 cups of flour) ( 120 cookies) = ( x cups of flour) ( 48 cookies)

                            330                  = 48 x

divide by 48          330/48.             = (48x)/48

                              6.875               = x , where x is the number of 

                                                         cups of flour.

So, we will need about 7 cups of flour. 

 

D.Y. Taylor

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