Question

Oblicz obwód koła o polu:
16 pi cm kwadratowego
4/9 pi m kwadratowego
0,25 pi mm kwadratowego
2 pi dm kwadratowego
3 km kwadratowego - Zadane.pl

Answer 1

Ob = 2πr
P = πr²

P = 16π cm²
16π cm² = πr² /:π
16cm² = r² /√
4cm = r
Ob = 2π*4cm
Ob = 8π cm

P = 4/9π m²
4/9π m² = πr² /:π
4/9m = r² /√
2/3 m = r
Ob = 2π*2/3m
Ob = 4/3π m

P = 0,25π mm²
0,25π mm² = πr² /:π
0,25mm² = r² /√
0,5mm = r
Ob = 2π*0,5mm
Ob = π mm

P = 2π dm²
2π dm² = πr² /:π
2 dm² = r² /√
√2 dm = r
Ob = 2π*√2dm
Ob = 2√2π dm

P = 3 km²
3km² = πr² /:3,14
0,995 km² ≈ r² /√
1km ≈ r
Ob = 2π*1km
Ob = 2*3,14*1km
Ob ≈ 6,28 km