Given data:
The cost of 10 ounces of popcorn is $2.50.
The expression for the given statement is,
[tex]\begin{gathered} 10\text{ ounces=\$2.50} \\ 1\text{ dollar=}\frac{10}{2.5}\text{ ounces} \\ =4\text{ ounces} \end{gathered}[/tex]Thus, 4 ounces of popcorn bought in a dollor.