Question

Dominique is buying water. She needs 2 liters. A​ half-liter of water costs ​$2.46. A 250​-milliliter container of water costs ​$1.48. What should Dominique buy so she gets 2 liters at the lowest​ price? Explain.

Answer 1

`\fbox{\begin{minipage}{15em}A half-liter of water costs 2.46$\end{minipage}}`

Explanation:

Dominique wants to buy
`2` liters of water.

Case 1:

A half-liter of water costs
`2.46`.

The
`2` half-liters is
`1` liter => The cost of a liter of water (
`A`) is calculated by multiply the cost of
`1` half-liter by
`2`:

`A = 2.46` x
`2` =
`4.92`

=> The cost of two liters:
`A_(1)` =
`A` x
`2` =
`4.92` x
`2` =
`9.84` $

Case 2:

A quarter-liter of water costs
`1.48`.

The 4 quarter-liters is
`1` liter => The cost of a liter of water (
`B`) is calculated by multiply the cost of
`1` quarter-liter by
`4`:

`B = 1.48` x
`4` =
`5.92`

=> The cost of two liters:
`B_(1) = 5.92` x
`2` =
`11.84` $

Compare
`A_(1)` and
`B_(1)`, the cost of second buying method is more expensive.

=> She should buy the water, in which a​ half-liter of water costs ​$
`2.46`

Hope this helps!

:)