5th grade math (word problems)
posted by Alex on .
Problem: A receipe for 4 dozen cookies requires 1 1/2 cups of flour. How much flour is needed for 1 dozen?
work: 4 divided by 1 1/2 = 4/1 x 3/2 =
4/1 x 2/3 = 8/3 cups of flour
Can you explain why i don't need to change 4 dozen to 48 and then divide by 1 1/2?

It's simpler to work with dozens than with 48. (Too many numbers)
You know you'll only need one fourth as much flour for one dozen cookies.
Let's work it this way. Cross multiply and solve for x.
4 / (1 1/2) = 1 / x
4x = 1 1/2
x = (1 1/2) / 4
x = 3/2 * 1/4
x = 3/8 cup 
thanks!

You're welcome.

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