Jawab:

1) 62,8 cm

2) 22 cm² & 154cm

3) 70 cm

4) 870 cm²

Penjelasan dengan langkah-langkah:

Rumus Lingkaran

Luas = π × r²

Keliling = 2 × π × r/π × D

r = ½ × D / D = 2 × r

Jika r-nya kelipatan 7 = π yg dipake 22/7

Jika r- nya bukan kelipatan 7 = π yg dipake 3,14

1. r = 10 cm (k = ?)

K = 2 × π × r

= 2 × 3,14 × 10

= 62,8 cm

_____________________

2. D = 14 cm (L = ?, K = ?)

r = ½ × D

r = ½ × 14 = 7 cm

L = π × r²

= 22/7 × 7 = 22 cm²

K = π × D

= 22/7 × 14

= 22 × 7 = 154 cm

_____________________

3. L = 3850 m² (D = ?)

L = π × r²

3850 = 22/7 × r²

3850 × 7/22 = r²

1225 = r²

√1225 = r

35 m = r

D = 2 × r

= 2 × 35 = 70 m

_____________________

4. r = 14 cm, s = 32 cm (Luas yg diarsir ?)

# Bangun besar (persegi)

L = s × s

= 32 × 32 = 1024 cm²

# Bangun kecil (lingkaran)

L = π × r²

= 22/7 × 14

= 22 × 7 = 154 cm²

# Luas yg arsir

Bangun besar - Bangun kecil

1024 - 154 = 870 cm²