Question

Which of the two is a better buy - `8` rolls costing `$2` or `10` rolls costing `$2.79`?

Answer 1

First package of `8` rolls costing `$2.00` is a better buy.

Explanation:

There are two packages.

First package of `8` rolls costs `$2.00` or `200` cents and

the price of `1` roll is `200/8=25` or `25` cents.

Second package of `10` rolls costs `$2.79` or `279` cents and

the price of `1` roll is `279/10=27.9` cents.

Hence first package of `8` rolls costing `$2.00` is a better buy.

Answer 2

`color(green)("8 at a total cost of $2.00 is the better deal.")`

Explanation:

The way to compare these is to determine the unit cost & compare.

`color(blue)("Unit cost condition 1")`

Consider `("cost")/("count") -> ($2.00)/8`

`($2.00)/8 -=($2.00-:8)/(8-:8)color(blue)( =($0.25)/1)`

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`color(blue)("Unit cost condition 2")`

Consider `("cost")/("count") -> ($2.79)/(10)`

`($2.79)/(10)-=($2.79-:10)/(10-:10) color(blue)(=($0.279)/1`
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`color(green)("By inspection condition 1 is the better deal")`