[CLASS 9] Mathematics MCQs on Surface Area of a Right Circular Cone

Mathematics Multiple Choice Questions on “Surface Area of a Right Circular Cone”.

1. The total surface area of a cone of base radius “r” and slanted height “l” is equal to __________
a) πrl + 2πr²
b) 2πrl + 2πr²
c) πrl + πr²
d) 2πr²

Answer: c
Clarification: Total surface area of a cone of base radius “r” and slanted height “l”
= Curved surface area of a cone + Base area of a cone
= πrl + πr².

2. What is the total surface area of a cone of radius 7cm and height 24cm? (Take π = (frac{22}{7}))
a) 710 cm²
b) 704 cm²
c) 700 cm²
d) 725 cm²

3. The curved surface area of a cone is 1980 cm² and its radius is 21cm, what is the slanted height of a cone? (Take π = (frac{22}{7}))
a) 25cm
b) 28cm
c) 35cm
d) 30cm

Answer: d
Clarification: We know that the curved surface area of a cone = πrl
πrl = 1980
(frac{22}{7}) * 21 * l = 1980
l = 30cm.