First rectangular garden:
length = 6 feet and width =4 feet
Perimeter of first garden =2(l+w) =2(6+4) =20 feet...........(1)
Second rectangular garden:
second rectangular garden has dimensions that are double the dimensions of the first garden
length =2* 6 =12 feet and width =2* 4 =8 feet
Perimeter of second garden =2(12+8) =2*20=40 feet

% change = (40-20)/20 *100 =100
% change =100%