gary needs to buy fencing to go around his rectangular dog pen, the pen is 8 ft long and has a perimeter of 36 ft. what is the width in ft of the pen? So this is third grade math and I think the answer is 6 but dont know how to explain it to my son.

Question

anonymous · Answer

the perimeter of a rectangle is 2L+2W with L=length and W=width 
you know that L=8
so you have 2(8)+2W=36
2x8 is 16 so
16+2W=36 if you minus 16 from each side 
16-16+2W=36-16
you get 2W=20
divide each side by 2
2W/2=20/2
W=10ft

anonymous · Answer

got it?