(b) Let curved surface area of first cone is CS1. and curved surface area of second cone is CS2. As per the question, CS1 = 3CS2 ⇒ πr1l1 = 3(πr2l2) ⇒ πr1l1 = 3πr2l2 ⇒ r1l1 = 3r2l2 ⇒ r1l1 = 3r2×3l1 ⇒ r1l1 = 9r2l1 ∴ r1 = 9r2 Now, required ratio of base area =