Question

A frame of width a surrounds a 5 by 7 inch photograph. Find the expression that represents the area of theframe in terms of a.

Answer 1

From the given question and diagram:

Total area = total length times

And,

$\text{Total width=(2a+5) times}$

So,

$\begin{gathered} (2a+5)(2a+7)=4a^2+14a+10a+35 \\ =4a^2+24a+35 \end{gathered}$

Then,

The original area which is 5 by 7 is 35

so,

$\begin{gathered} 4a^2+24a+35=4a^2+24a+35-35 \\ =4a^2+24a \end{gathered}$

Hence, the correct option is B.