Question

In the morning, Marco sold 12 cups of lemonade for $3. By the end of the day, he had earned $9. How many cups of lemonade did he sell in all? Kaycee wrote the proportion StartFraction 12 over 3 EndFraction = StartFraction 9 over c EndFraction for this situation.

Answer 1

Kaycee did not keep lemonade and dollars in corresponding positions in the ratios of the proportion. The proportion should be 12/3=c/9 or it could be written 3/12=9/c. Dollars should be in the same position and cups should be in the same position across ratios.

Answer 2

36 cups of lemonade

Explanation:

12 cups of lemonade = $3

By the end of the day, he had earned $9

This means

c cups of lemonade = $9

How many cups of lemonade did he sell in all?

This is the correct proportion:

Cups of lemonade : price

12 : 3 = c : 9

12 / 3 = c / 9

Cross product

12*9 = 3*c

108 = 3c

c = 108/3

= 36

c = 36 cups of lemonade

He had sold 36 cups of lemonade