Question

We have a 17 by 20-foot garden. We want to pour cement for a sidewalk 3 feet wide around the garden. To make the forms for the cement, we will need to buy some 2 by 4 inch lumber. How many feet of 2 by 4 inch lumber will we need just for the perimeter of the walk? (Consider both inside and outside perimeter.)

Answer 1

Perimeter = 2(width+length)

For garden,
width=17'
length=20'
perimeter(inside)=2(17+20)=74'

For outside of sidewalk,
width = 17+2*3'=23'
length= 20+2*3'=26'
perimeter(outside)=...

Can you calculate the outside perimeter and add up the two perimeters?

Answer 2

172