I don't understand this

Question

"A plot is 60m long and 40m wide. A path 3m wide is to be constructed around the plot . find the area of the path" This question is in my maths book and the answer is 636m square but I don't understand how

Answer 1

$$636 = [(60+2\times 3) \times (40 + 2\times 3)] - (60\times 40) $$

That is, the area that is added to the plot after paving a path around plot that is $3$ meters wide is equal to $636$ m$^2$: the area of the new 3m wide path surrounding the original plot.