Question

Please help me ! ! !
A Circle has a radius of 12cm. Find the percentage change in the area of the circle if the radius increases by 20%

Answer 1

okay so I believe that if you increase the radius by 20%

so if we represent the original radius as r
the new radius becomes 1.20r

Answer 2

so... 12 x 1.20?

Answer 3

so I think we would approach it like this. we substitute 1.20r into the formula for the area.

\[A = \pi*r^{2}\]

\[A_{2} = \pi*(1.20r)^{2}\]

Answer 4

@sugarMochi \[A_{2} = 1.44*\pi*r^{2} | A_{1} = \pi*r^{2}\]

Answer 5

@SugarMochi what do you realize about the new area?

Answer 6

44 more than the original area ?

Answer 7

44% more

Answer 8

oHHHH i get it now !!!! Thankyou so so so much

Answer 9

do you see what I did?

Answer 10

mhmmm yep yep

Answer 11

let's check again we can actually put in 12 cm and check our answer

Answer 12

\[(12cm)^{2}*\pi = 144\pi = area \]

\[(12*1.20)^{2} = 207\pi = area \]

Answer 13

so if we multiply 144pi *(1.44) we end up getting 207pi

Answer 14

@SugarMochi we actually did not have to plug in any numbers we just used the fact that a 20% increase was 1.20 then we plugged it into the formula for area.

Answer 15

yeessss i get it now. Thankyou lots and lots and lots :')))

Answer 16

no problem