word problem

Question

A cookie recipe calls for 2 cups of milk to be mixed with 1.5 cups of flour. If Jane wants to make a larger batch, how much flour would be needed to mix with 3 cups of milk?

Answer 1

I will show you how to do this problem 3 ways...

YOU get to pick which one you like the best!

 

---------------- Option 1 : percents -------------------------------------------------------

 

The percent increase of milk is 100% * (3-2)/2 = 100%*(1/2) = 50%

 

So the flour must also be increased by 50% = 0.5

100% + 50% = 150% = 1.5

 

So the amount of flour needed is 1.5 cups x 1.5 = 2.25 cups = 2 and 1/4 cups of flour

 

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Here's another way to view the same problem.

The ratio given by the recipe is 1.5 cups of flour per 2 cups of milk.

 

That is the same as 0.75 cups of flour per 1 cup of milk. <--- divides both by 2, where 1.5/2 = 0.75

 

So for 3 cups of milk, 3 * 0.75 cups of flour is needed which is 2.25 cups of flour.

 

 

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Finally,  a third option is just set up an equal proportion:

 

 milk           2              3

------ = ---------- = ----------

 flour          1.5            ?

 

 

 cross multiplication: 2 * ? = 3 * 1.5

 

                              2 * ? = 4.5

 

                              ? = 4.5/2 = 2.25