The surface area of a sphere is directly proportional to the square of its radius. Find: a)the change in surface area of radius decreases 19% b) The change in radius of the surface area is trebled

a: 34%

b: couldn't find the answer

Step-by-step explanation:

first we put the radius as r

we know surface area is 4pirsquared

so then we minus percent which is 119 so it is 81/100

square that fraction which will result 6561/10000

now we put in and equation of 4pirsquared -4pirsquared multiply 6561/10000 divide this all by 4pirsquared to get 3439/10000 or 0.3439 change it to %

34.39%

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