Let the side of the first square be x and that of another be y.
Case(i)
Area of square =(Side)2
⇒x2+y2=640m2…Eq(i)
Case(ii)
Difference of their perimeter =64 m
So,
⇒4x−4y=64
⇒x−y=16
⇒x=16+y
Put the value of x in Eq(i) we get,
⇒(16+y)2+y2=640
⇒256+y2+32y+y2=640
⇒2y2+32y=384
⇒y2+16y=192
⇒y2+24y−8y−192=0
⇒y(y+24)−8(y+24)=0
∴y=8
Hence, x=16+8=24
So, the length of the required sides are 8 m and 24 m.