Analyzing Functions in Context

Let $l$ and $w$ represent the length and the width of a rectangle, respectively. It is given that, for an A series paper, the length is $1.4$ times the width. We can express this algebraically as an equation. $$\begin{array}{c}l=1.4w\end{array}$$ Recall that the formula for the area of a rectangle is $A=l\cdot w.$ Let's substitute $1.4w$ for $l$ into this formula to express the area in terms of the width, $w.$ Thus, a paper in the A series with the width $w$ has the area $A=1.4w^2.$