CBSE 10th Math Sample Paper 2019 | Q29

This 2019 CBSE class 10 Maths 4 mark question is from Surface Areas. Concept covered in this 4-mark question that appeared in the 2019 sample question paper: Computing surface area of frustum of cone.

Question 29: The radii of the circular ends of a bucket of height 24 cm are 15 cm and 5 cm. Find the area of its curved surface.

Video Explanation

Explanatory Answer

Height = BC = 24 cm
R = CE = 15 cm
r = AB = 5 cm
Curved Surface area of bucket (frustum of cone) = π × (R + r) × l

Step 1: Find slant height 'l' – AE is the slant height
Draw AD perpendicular to CE. ΔADE is a right triangle.
AD = BC = 24 cm
CD = AB = 5 cm
Therefore, DE = 15 – 5 = 10 cm
AE² = AD² + DE²
AE² = 24² + 10² = AE² = 576 + 100
AE =\\sqrt{676}) = 26

Curved Surface area of bucket (frustum of cone) = π × (R + r) × l
= \\frac{22}{7}) × (15 + 5) × 26 = 1634.3 cm²