How can i solve this tough question of class 9th ncert of Surface areas and Volumes of math of exercise 13.4 of question no.4 . Give me the best and simple way for solving this question. The radius of a spherical balloon increases from 7cm to 14cm as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases.
AnilSinghBoraGuru
The radius of a spherical balloon increases from 7cm to 14cm as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases. Q.4
Share
Let r1 and r2 be the radii of spherical balloon and spherical balloon when air is pumped into it respectively. So
r1 = 7cm
r2 = 14 cm
Now, Required ratio = (initial surface area)/(Surface area after pumping air into balloon)
= 4r12/4r22
= (r1/r2)2
= (7/14)2 = (1/2)2 = ¼
Therefore, the ratio between the surface areas is 1:4.