Ex 11.4, 9 - Chapter 11 Class 9 Surface Areas and Volumes

Last updated at April 16, 2024 by Teachoo

Transcript

Ex 11.4, 9
Twenty seven solid iron spheres, each of radius r and surface area S are melted to form a sphere with surface area S . Find the
radius r of the new sphere,
Whenever one shape is melted to another shape,
volume remains constant
Volume of 27 sphere of radius r = Volume of big sphere of radius r
27 (4/3 r3) = 4/3 (r )3
27r3 = r 3
r 3 = 27r3
r 3 = (3r)3
r = 3r.
Ex 11.4, 9
(ii) ratio of S and S .
/ = ( )/( ^ )
= 4 2/(4 ( ^ )^2 )
= 2/( ( ^ )^2 )
= 2/(3 )2
= 2/9 2
= 1/9
Therefore, ratio of S & S is 1 : 9

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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