Question

the table below gives the price for different numbers of books. is the price proportional to the number of books? number of books 1- price 3 3 books price-9 4 books price-12 7 books price 18

Answer 1

Two quantities are proportional if the ratio between those quantities is always the same.

Find the ratio of price/number of books for each row in the table:

`\begin{gathered} (3)/(1)=3 \\ (9)/(3)=3 \\ (12)/(4)=3 \\ (18)/(7)=2.57\ldots \end{gathered}`

We can see that the ratio price:books is 3 if the number of books is 1, 3 or 4 but it is a different ratio when the number of books is 7.

Therefore, the price is not proportional to the number of books.

Sidenote:

If the number of books on the last row was 6 instead of 7, then the ratio would still be 3 and the price would be in fact proportional. Make sure that it is not a printing error of the problem sheet.