The circumference of a circle is 25.12, the radius is increased by 1 / 4, and the area is increased ()

The circumference of a circle is 25.12, the radius is increased by 1 / 4, and the area is increased ()

What is the radius of the circle
(25.12/3.14)/2=4
Now the radius is
4*(1+1/4)=5
Area increase
5*5*3.14-4*4*3.14=28.26

The circumference of a circle is 25.12cm, and the radius of a circle is______ The area is______ What is the circumference of a semicircle______ ．

The radius of the circle is 4cm, the area is 50.24cm, and the circumference of the semicircle is 20.56cm

If the radius of a circle increases by a quarter, how much does the circumference of the circle increase? How much does the area increase?
Who is the most reasonable is the best.

The radius of the circle increases by a quarter, the circumference of the circle increases by a quarter, the area increases by 9 / 16, the circumference formula of the circle is 2 π R, the radius increases by a quarter, and the circumference is: 2 π (1 + 0.25) r = 2 π R × (1 + 0.25) = 2 π R + 2 π R × 0.25, then it is 2 π R × 0.25 more than your original 2 π R, that is, a quarter of the multi perimeter