Mary is making some shirts for her school's drama department. the fabric store has 3 1/6 yards of the fabric she wants in stock. but this quantity of fabric can make only 1 1/3 shirts. what length of fabric does mary need to buy if she wants to sew 2 shirts?

The answer is 4 3/4 yards of the fabric.

This can be calculated using the proportion.
If the 3 1/6 yards of the fabric is enough for 1 1/3 shirts, how many yards are necessary of 2 shirts:


Let's express 3 1/6 as 19/6:


Similarly, 1 1/3 = 4/3:


Now, let's use this in the proportion:



Crossing the products:

⇒ 
⇒ 

⇒ 

Therefore, Mary needs in total 4 3/4 yards of the fabric.