Ex 11.3, 7 - Chapter 11 Class 9 Surface Areas and Volumes

Last updated at April 16, 2024 by Teachoo

Transcript

Ex 11.3 , 7
A right triangle ABC with sides 5 cm, 12 cm and 13 cm is revolved about the side 12 cm. Find the volume of the solid so obtained.
Let ABC with right angle at B.
AC will be hypotenuse, AC = 13 cm
And AB = 12 cm, BC = 5 cm
We revolve ABC about the side AB (= 12 cm)
, we get a cone as shown in the figure.
Radius = r = 5 cm,
& Height = h = 12 cm
Volume of solid so obtained = 1/3 r2h
= (1/3 " " 5 5 12) cm3
= (1 " " 25 4) cm3
= 100 cm3 .

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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