Final answer:
Morgan's purchase of 11 books, which was 5% of the total, allows us to set up the proportion 11/x = 5/100. Solving for x by cross-multiplying and dividing gives us a total of 220 books sold at the school book sale.
Step-by-step explanation:
The student's question can be solved by setting up a simple proportion to find out the total number of books sold at the school book sale.
If Morgan bought 11 books which represent 5% of the total number of books, we can represent this information as a ratio 11 (number of books Morgan bought) to x (total number of books sold), which equals 5 to 100 (as percentages are parts of 100). This setup can be represented as 11/x = 5/100.
By solving this proportion, we can find the total number of books sold.
To solve the proportion, we cross-multiply: 11 × 100 = 5 × x.
This results in 1100 = 5x. To find x, we divide both sides by 5, which gives x = 1100 / 5.
Calculating this gives us x = 220.
Therefore, 220 books were being sold at the school book sale.