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.

Answers (1)

Firstly we need to calculate the slant height of cone :

                                                      l^2\ =\ r^2\ +\ h^2

or                                                         =\ (0.7)^2\ +\ (2.4)^2

or                                                    l^2\ =\ 6.25

or                                                   l\ =\ 2.5\ cm

Now, the total surface area of solid can be calculated as :

The surface area of solid   =   Surface area of cylinder  +   Surface area of cone   +    Area of base of the cylinder

 The surface area of the cylinder is  =\ 2 \pi rh

or                                          =\ 2 \pi \times 0.7\times 2.4

or                                         =\ 10.56\ cm^2

Now, the surface area of a cone  =\ \pi rl

or                                         =\ \pi \times 0.7\times 2.5

or                                         =\ 5.50\ cm^2

And the area of the base of the cylinder is   =\ \pi r^2

or                                                      =\ \pi \times 0.7\times 0.7

or                                                      =\ 1.54\ cm^2

Thus required area of solid  =  10. 56  +  5.50  +  1.54   =  17.60  cm2.

Thus total surface area of remaining solid to nearest cm2 is 18 cm2.

Preparation Products

JEE Main Rank Booster 2021

This course will help student to be better prepared and study in the right direction for JEE Main..

₹ 13999/- ₹ 9999/-
Buy Now
Rank Booster NEET 2021

This course will help student to be better prepared and study in the right direction for NEET..

₹ 13999/- ₹ 9999/-
Buy Now
Knockout JEE Main April 2021 (Subscription)

An exhaustive E-learning program for the complete preparation of JEE Main..

₹ 4999/-
Buy Now
Knockout NEET May 2021

An exhaustive E-learning program for the complete preparation of NEET..

₹ 22999/- ₹ 14999/-
Buy Now
Knockout NEET May 2022

An exhaustive E-learning program for the complete preparation of NEET..

₹ 34999/- ₹ 24999/-
Buy Now
Exams
Articles
Questions