The perimeter of rectangle 1 is equal to the perimeter of rectangle 2, that is

(5a+3a)×2=(3b+b)×2 gives 2a = b.

The area of the rectangle 1 is 5a×3a= 15a? =50, so 3a? = 10

:3b×b=3b？

Because b=2a, 3b? =3×4a？ =4×3a？ =4× 10=40

That is, the area of rectangle No.2 is 40 square centimeters.