Exemplo 9.15 de Prealgebra, 9.2 Solve Money Applications

Solve Money Applications: exemplo 9.15

Problema e solução em inglês, como no livro original.

Monica paid $$10.44$ for stamps she needed to mail the invitations to her sister's baby shower. The number of $49-cent$ stamps was four more than twice the number of $8-cent$ stamps. How many $49-cent$ stamps and how many $8-cent$ stamps did Monica buy?

Resolva no papel primeiro. Depois abra a solução um passo de cada vez e pare assim que conseguir terminar sozinho.

Solução

The type of stamps are $49-cent$ stamps and $8-cent$ stamps. Their names also give the value.

“The number of $49$ cent stamps was four more than twice the number of $8$ cent stamps.”

$\begin{matrix} Let x = number of 8-cent stamps \\ 2 x + 4 = number of 49-cent stamps \end{matrix}$

Type	$Number$	$Value ($)$	$Total Value ($)$
$49-cent$ stamps	$2 x + 4$	$0.49$	$0.49 (2 x + 4)$
$8-cent$ stamps	$x$	$0.08$	$0.08 x$
			$10.44$

Write the equation from the total values.	$0.49 (2 x + 4) + 0.08 x = 10.44$
Solve the equation.	$0.98 x + 1.96 + 0.08 x = 10.44$ $1.06 x + 1.96 = 10.44$ $1.06 x = 8.48$ $x = 8$
Monica bought 8 eight-cent stamps.
Find the number of 49-cent stamps she bought by evaluating.	$2 x + 4 for x = 8 .$
	$2 x + 4$ $2 \cdot 8 + 4$ $16 + 4$ $20$
Check. $8 (0.08) + 20 (0.49) \overset{?}{=} 10.44$ $0.64 + 9.80 \overset{?}{=} 10.44$ $10.44 = 10.44 ✓$

Monica bought eight $8-cent$ stamps and twenty $49-cent$ stamps.

Sua vez

O Try It do livro logo depois deste exemplo: mesma ideia, outros números. Só a resposta é dada.

Eric paid $$16.64$ for stamps so he could mail thank you notes for his wedding gifts. The number of $49-cent$ stamps was eight more than twice the number of $8-cent$ stamps. How many $49-cent$ stamps and how many $8-cent$ stamps did Eric buy?

Como foi?

Sua vez

O Try It do livro logo depois deste exemplo: mesma ideia, outros números. Só a resposta é dada.