A) Luas = πr²

78,5 = 3,14r²

78,5 : 3,14 = r²

25 = r²

r² = 25

r = √25

r = 5 m

Diameter = Jari – jari ( r ) × 2

= 5 × 2

= 10 m

B) Luas = πr²

792/7 = 22/7 × r²

792/7 : 22/7 = r²

792/7 × 7/22 = r²

36 = r²

r² = 36

r = √36

r = 6 cm

Diameter = Jari – jari ( r ) × 2

= 6 × 2

= 12 cm

C) Luas = πr²

452,16 = 3,14 × r²

452,16 : 3,14 = r²

144 = r²

r² = 144

r = √144

r = 12 m

Diameter = Jari – jari ( r ) × 2

= 12 × 2

= 24 m

D) Luas = πr²

2.200/7 = 22/7 × r²

2.200/7 : 22/7 = r²

2.200/7 × 7/22 = r²

100 = r²

r² = 100

r = √100

r = 10 dm

Diameter = Jari – jari ( r ) × 2

= 10 × 2

= 20 dm

E) Luas = πr²

5.544 = 22/7 × r²

5.544 : 22/7 = r²

5.544 × 7/22 = r²

1.764 = r²

r² = 1.764

r = √1.764

r = 42 cm

Diameter = Jari – jari ( r ) × 2

= 42 × 2

= 84 cm

√ = akar kuadrat