NCERT Solutions for Class 10 Maths Chapter 13

Important NCERT Questions

Surface areas and Volumes,

NCERT Books for Session 2022-2023

CBSE Board and UP Board Others state Board

EXERCISE 13.1

Page No:245

Questions No:8

# From a solid cylinder whose height is 2.4 cm and diameter 1.4 cm, a conical cavity of the same height and same diameter is hollowed out. Find the total surface area of the remaining solid to the nearest cm2.

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Height of conical part = Height of cylindrical part (h) = 2.4 cm

Diameter of cylindrical part = 1.4 m, so, the radius of cylindrical part (r) = 0.7 m

Slant height of cylindrical part (l) = √(r²+ h²)

= √((0.7)² + (2.4)²) = √(0.49 + 5.76) = √(6.25) = 2.5

The total surface area of the remaining solid

= CSA of cylindrical + CSA of conical part + Area of base of cylinder

= 2πrh + πrl + πr²

= 2 × 22/7 × 0.7 × 2.4 + 22/7 × 0.7 × 2.5 + 22/7 × 0.7 × 0.7

= 4.4 × 2.4 + 2.2 × 2.5 × 0.7 = 10.56 + 5.50 + 1.56 = 17.60 cm².