Question

if the radius of a circle is increased by 10% then the area is increased by?

Answer 1

pi*r^2

Answer 2

will the increase in area be 0.03% @.Sam. ?

Answer 3

take the initial radius to be r...then enlarged radius is r+r/10=11r/10...now area=\[\Pi*radius ^{2}\] .....so u have initial area as 3.14r^2...and final as 3.14*121r^2/100....so increase is 21/100*pi*r^2...thats 21 percent increase

Answer 4

how it's 11r? @amriju i didnt get u :(

Answer 5

10 pecent increase inr so radius=r+10/100*r=11r/10

Answer 6

A=pi r^2 r/dr =0.1
dA/A=?
A= pi *r^2 1)
dA/dr =2 pi r 2)
dA= 2 pi r dr 3)
dividing 3 by 1
dA/A =2r/dr
dA/A= 2* 0.1=0.2
20 percent

Answer 7

@girlish

Answer 8

listen @amriju it wud be 121% increase
isn't it?

Answer 9

no....ur initial area is pi*r^2 write dat as 100/100*pi*r^2....can u..?..now final area is 121pi*r^2/100...so wats the increase..?...21/100*pi*r^2...rite..?...so percent increase=21

Answer 10

not 21 there might be small error it should be 20 percent

Answer 11

if u r doing by taking initial values first then there could be some error

Answer 12

A is prportinal to sqaure of radius that means area will increase by factor of 2

Answer 13

r/dr=10 dear...r is obviously greater than dr...how can u write 0.1

Answer 14

@Fazeelayaz

Answer 15

well it's 10 percent of the original value 10/100=0.1

Answer 16

sorr y i have made mistake it's dr/r

Answer 17

A=pi r^2 dr/r =0.1
dA/A=?
A= pi *r^2 1)
dA/dr =2 pi r 2)
dA= 2 pi r dr 3)
dividing 3 by 1
dA/A =2dr/r
dA/A= 2* 0.1=0.2
20 percent

Answer 18

now it's correct

Answer 19

21 percent is not wrong u took initial values of r that's fine ok but there would be some error in it since pi is irrational u can't wright whole value of it down

Answer 20

do get me @amriju

Answer 21

no...coz..pi is going to cancel...even if took pi=12147.2147....the answer wud not hav varied...

Answer 22

*even if I

Answer 23

ok

Answer 24

:)

Answer 25

now lets take r = 1 ok A=pi r^2
A=pi
after increasing by 10 percent area is
A2= pi(1.1)^2=pi*1.21
A2-A1=0.21 ok

Answer 26

it's 21 percent take it that's not wrong but correct way is to do by differentiation

Answer 27

no....differentiation is the process of studing rate of change...not change itself...in any case...no method is wrong as long as it works for any genaralised value...

Answer 28

i think u should get a medal

Answer 29

oh...thnks....