Jawaban:

a. L = 154 cm²

Diameter = 14 cm

Jari-jari = 7 cm

b. L = 314 cm²(π=3,14)

Diameter = 20 cm

Jari-jari = 10 cm

c. L = 616 cm²

Diameter = 28 cm

Jari-jari = 14 cm

d. L = 1.256 cm²(π=3,14)

Diameter = 40 cm

Jari-jari = 20 cm

e. L = 1.386 cm²

Diameter = 42 cm

Jari-jari = 21 cm

f. L = 3.850 cm²

Diameter = 70 cm

Jari-jari = 35 cm

Penyelesaian

a) L = π x r²

154cm² = 22/7 x r²

r² = 154 cm² : 22/7

r² = 154 cm² x 7/22

r² = 49 cm²

r = √49 cm²

r = 7 cm

d = 2 x r

d = 2 x 7 cm

d = 14 cm.

b) L = π x r²

314 cm² = 3,14 x r²

r² = 314 cm² : 3,14

r² = 100 cm²

r = √100 cm²

r = 10 cm

d = 2 x r

d = 2 x 10 cm

d = 20 cm.

c) L = π x r²

616 cm² = 22/7 x r²

r² = 616 cm² : 22/7

r² = 616 cm² x 7/22

r² = 196 cm²

r = √196 cm²

r = 14 cm

d = 2 x r

d = 2 x 14 cm

d = 28 cm.

d) L = πr²

1.256 cm² = 3,14 x r²

r² = 1.256 cm² : 3,14

r² = 400 cm²

r = √400 cm²

r = 20 cm

d = 2 x r

d = 2 x 20 cm

d = 40 cm.

e) L = π x r²

1.386 cm² = 22/7

r² = 1.386cm² : 22/7

r² = 1.386 cm² × 7/22

r² = 441 cm²

r = √441 cm²

r = 21 cm

d = 2 x r

d = 2 x 21 cm

d = 42 cm.

f) L = π x r²

3.850 cm² = 22/7

r² = 3.850 cm² : 22/7

r² = 3.850 cm² × 7/22

r² = 1.225 cm²

r = √1.225 cm²

r = 35 cm

d = 2 x r

d = 2 x 35 cm

d = 70 cm.

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