Question

0.49f + 0.34p = 5.00 solve for f and p

Answer 1

Since the total cost must be $5, the we have the following equation which relates the postacard and first class staps:

`0.49f+0.34p=5`

where f denotes the number of first class stamps and p the nunber of postcard stamps.

Now, we need to solve for f. Then, by moving 0.34p to the right hand side, we have

`0.49f=5-0.34p`

and by dividing both sides by 0.49, we get

`f=(5)/(0.49)-(0.34)/(0.49)p`

or equivalently

`f=(5-0.34p)/(0.49)`

Now, we need to solve for p. Then, by moving 0.49f to the right hand side, we obtain

`0.34p=5-0.49f`

and by dividing both sides by 0.34, we get

`p=(5-0.49f)/(0.34)`

Finally, we have that f=7 and we need to find p. In this regard, this last equation must help us. By substituting f=7, we have

`p=(5-0.49(7))/(0.34)`

which gives

`\begin{gathered} p=(5-3.43)/(0.34) \\ p=(1.57)/(0.34) \\ p=4.617 \end{gathered}`

By rounding up this result, the number of postcard stamp is 5.

In summary, the answers are

`\begin{gathered} f=(5-0.34p)/(0.49) \\ p=(5-0.49f)/(0.34) \\ \text{and} \\ 5\text{ postcard stamps} \end{gathered}`