Jawaban:

Penjelasan dengan langkah-langkah:

a)

Dik:Jari jari (r) = 15 cm

Dit:Keliling dan luas lingkaran?

Jawab:

keliling lingkaran

\begin{gathered}k = 2 \times \pi \times r \\ \: \: \: = 2 \times 3.14 \times 15 \: cm \\ \: \: \: = 6.28 \times 15 \: cm \\ \: \: \: =94.2 \: cm\end{gathered}

k=2×π×r

=2×3.14×15cm

=6.28×15cm

=94.2cm

Luas lingkaran

\begin{gathered}l = \pi {r}^{2} \\ \: \: = 3.14 \times 15 cm\times 15 cm\\ \: \: = 47.1 \times 15 \: cm \\ \: \: = 706.5 \: cm\end{gathered}

l=πr

2

=3.14×15cm×15cm

=47.1×15cm

=706.5cm

b)

dik : Diameter = 40 cm

Dit : Keliling dan luas lingkaran ?

jawab :

kelilling lingkaran:

\begin{gathered}k = \pi \times \: d \\ \: \: \: =3.14 \times40 \: cm \: \\ \: \: \: =125.60 \: cm \: \end{gathered}

k=π×d

=3.14×40cm

=125.60cm

Luas lingkaran:

D=40 cm -> R= 20 cm

\begin{gathered}l = \pi \times {r}^{2} \\ \: \: = 3.14 \times 20 \: cm \times 20 \: cm\\ \: \: = 62.8 \times 20 cm\\ \: \: = 1256 \: cm\end{gathered}

l=π×r

2

=3.14×20cm×20cm

=62.8×20cm

=1256cm

C)

Dik: jari jari (r)= 28

Dit :Kelilling dan luas ?

jawab:

keliling lingkaran:

\begin{gathered}k = 2 \times \pi \times r \\ \: \: \: = 2 \times \frac{22}{7 } \times 28 \\ \\ \: \: \: = 2 \times 22 \times 4 \\ \: \: \: = 2 \times 88\\ \: \: \: = 176 \: cm\end{gathered}

k=2×π×r

=2×

7

22

×28

=2×22×4

=2×88

=176cm

Luas lingkaran

\begin{gathered}l = \pi {r}^{2} \\ \\ = \frac{22}{7} \times 28 \times 28 \\ \\ = 22 \times 4 \times 28 \\ = 88 \times 28 \\ = 2464 \: cm\end{gathered}

l=πr

2

=

7

22

×28×28

=22×4×28

=88×28

=2464cm

D)

Dik : diameter (D) = 42

dit: keliling dan luas lingkaran ?

keliling lingkaran:

\begin{gathered}k = \pi \times d \\ \\ = \frac{22}{7} \times 42 \\ \\ =22 \times 6 \\ = 132 \: cm \: \end{gathered}

k=π×d

=

7

22

×42

=22×6

=132cm

luas lingkaran

D=42 cm -> r= 21 cm

\begin{gathered}l = \pi \times {r}^{2} \\ \\ = \frac{22}{7} \times 21cm \times 21cm \\ \\ = 22 \times 3 \times 21 cm\\ = 66 \times 21cm \\ = 1386 \: cm\end{gathered}

l=π×r

2

=

7

22

×21cm×21cm

=22×3×21cm

=66×21cm

=1386cm

e)

dik:Jari jari (r)=100 cm

Dit : keliling dan luas ?

jawab:

keliling lingkaran

\begin{gathered}k = 2 \times \pi \times r \\ \\ = 2\times 3.14\times 100cm \\ = 6.28\times 100 \: cm \\ = 628 \: cm\end{gathered}

k=2×π×r

=2×3.14×100cm

=6.28×100cm

=628cm

luas lingkaran :

\begin{gathered}l = \pi {r}^{2} \\ \\ = 3.14 \times 100 \times 100 cm\\ = 314 \times 100cm \\ = 31400 \: cm\end{gathered}

l=πr

2

=3.14×100×100cm

=314×100cm

=31400cm

Detail jawaban:

Mapel:Matematika

kelas:8

Bab:Lingkaran

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