In the morning, Marco sold 12 cups of lemonade for $3. By the end of the day, he had earned $9. How many cups of lemonade did he
sell in all? Kaycee wrote the proportion StartFraction 12 over 3 EndFraction = StartFraction 9 over c EndFraction for this situation. Identify the error and give two ways to write the proportion correctly.
1. If Marco sold 12 cups of lemonade for 3$, we would divide 12 cups and how much he earned from the 12 cups (3$). 12/3 = 4
2. By the end of the day, Marco earned $9. So, 4 cups = 1$. To break it down, 1$ = 100 cents and 100 cents divided by 4 is 25 cents. Cups to Cost. ( 4 : 1 ) and/or ( 1 : 0.25 )
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.
