Question

If the radius of a circle is multiplied by 3 what happens to the area of a circle

Answer 1

Area equals pi multiplied by (r squared) 
Therefore; 
if the Radius is multiplied by 3 
Area = pi multiplied by (r*3)^2 
Area = pi multiplied by 9 r squared 
Thus; 
multiplying the radius by 3 increases the area by 3 squared or 9 
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==> The area increases by a factor of 9 <== 
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I hope this is helpful.

Answer 2

area = πr^2 so the equation changes to area = π(3r)^2