Question

The cost to mail a package is 5.00. Noah has postcard stamps that are worth 0.34 and first-class stamps that are worth 0.49 each. An equation that represents this is 0.49f + 0.34p = 5.00Solve for f and p.If Noah puts 7 first-class stamps, how many postcard stamps will he need?

Answer 1

`\begin{gathered} f=(5.00-0.34p)/(0.49) \\ p=(5.00-0.49f)/(0.34) \\ p=4.618\approx5\text{ postcard stamps} \end{gathered}`

Step-by-step explanation

The equation that represents the situation is:

`0.49f+0.34p=5.00`

To solve for f, make f the subject of the formula from the equation:

`\begin{gathered} 0.49f=5.00-0.34p \\ \Rightarrow f=(5.00-0.34p)/(0.49) \end{gathered}`

To solve for p, make p the subject of the formula from the equation:

`\begin{gathered} 0.34p=5.00-0.49f \\ \Rightarrow p=(5.00-0.49f)/(0.34) \end{gathered}`

To find how many postcard stamps Noah will need if he puts 7 first-class stamps, solve for p when f is equal to 7.

That is:

`\begin{gathered} p=(5.00-(0.49\cdot7))/(0.34) \\ p=(5.00-3.43)/(0.34)=(1.57)/(0.34) \\ p=4.618\approx5\text{ postcard stamps} \end{gathered}`