A domino consists of two congruent squares placed side by side. the perimeter of the domino is 60 units. what is the area of the domino, in square units?
Suppose that the Domino's short side measures l units. Then it's long side measures 2l units, and the Domino's total perimeter is 6l=60. Thus l =10 and the Domino's area is 10 x 20=200 square units.
So say the dominoes' short side is x. Then the long side is 2x, so altogether there is 6x. So 6x=60, so x=10. So the area is 10*(10*2), which is 10*20 which is 200.