Sides of two similar triangles are in the ratio 4 : 9. Areas of these triangles are in the ratio :
(A) 2 : 3
(B) 4 : 9
(C) 81 : 16
(D) 16 : 81
Answer is (D) 16 : 81
∴ (4)2 : (9)2 = 16 : 81.