Question

A man ordered 3 times as many boxes of ballpoint pens as boxes of felt-tip pens. Ballpoint pens cost $4.31 per box, and felt-tip pens cost $3.42. If the man's order of pens totaled $98.10. how many boxes of each type pen did he buy? How many boxes of felt-tip pens did he buy? How many boxes of ballpoint pens did he buy?

Answer 1

let x be the number of ballpoint boxes and y the number of felt tip boxes

so we get

`\begin{gathered} \begin{cases}4.31x+3.42y=98.10 \\ x=3y\end{cases}\rightarrow \\ 4.31\cdot3y+3.42\cdot y=98.10 \\ 12.93y+3.42y=98.10 \\ 16.35y=98.10 \\ y=(98.10)/(16.35)=6 \end{gathered}`

so we get that the number of felt tip boxes is 6, and therefore the number of ballpoint boxes is 6*3=18