area of parallogram now = 8*10 = 80 square units
if the sides are multiplied by 4 the new dimensions would be
8*4 = 32, 10*4 = 40
area would be 32 *40 = 1280 square units
1280 /80 = 16
the area multiplied 16 times which is the multiple squared ( 4^2 = 16)