Question

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Answer 1

ok so first u need to know, how fast the area is growing

Answer 2

it went from 0 to an area of pi*10^2 in 4 secs
so from 0 to 100 pi in 4 secs

Answer 3

but its not as simple as you think

Answer 4

there are 2 ways to do this

Answer 5

the radius is a linear change but the area is not a linaer change

Answer 6

so we are better off looking at the radius
radius is 10 in 4 secs
so 10/4=2.5 radius/second