percent change=change/original times 100
perimiter
if length and width double then the perimiter doubles
because
P=2(L+W)
L=10
W=6
old one
P=2(10+6)
P=2(16)
P=32
new one
20 and 12
P=2(20+12)
P=2(32)
P=64
percent change=change/original times 100
change=64-32=32
original=32
percent change=32/32 times 100=100%
area
old are=legnth tiems wdith =6 times 10=60
nwe one
area=12 times 20=480
change is 240-60=180
percent change=180/60 times 100=3 times 100=300
perimiter is 100% change
area is 300% change