$\begin{aligned}11.\quad&\textrm{Sebuah lintasan lari berbentuk lingkaran yang}\\ &\textrm{berdiameter 56 meter. Banyak putaran yang harus}\\ &\textrm{dilakukan pelari jika ia ingin menempuh jarak}\\ &\textrm{902 meter adalah}\:....\\ &\text{a}.\quad 5\displaystyle \frac{3}{4}\quad \textrm{putaran}\\ &\text{b}.\quad 5\displaystyle \frac{1}{2}\quad \textrm{putaran}\\ &\text{c}.\quad 5\displaystyle \frac{1}{4}\quad \textrm{putaran}\\ &\text{d}.\quad 5\displaystyle \frac{1}{8}\quad \textrm{putaran}\\\\ &\textrm{Jawab}:\quad \textbf{d}\\ &\textrm{Diketahui bahwa lingkaran dengan}\:\: K=\pi d\:\: \textrm{meter} \\ &\textrm{maka, K}=\displaystyle \frac{22}{7}.56\:\: \textrm{meter}=176\:\: \textrm{meter}\\ &\textrm{Sehingga banyak putaran yang perlu dilakukan adalah}\\ &=\displaystyle \frac{902}{176}=5\displaystyle \frac{1}{8}\:\: \textrm{putaran}\end{aligned}$.
$\begin{aligned}12.\quad&\textrm{Perhatikan gambar berikut}\end{aligned}$.
$\begin{aligned}\qquad&\textrm{Berdasarkan gambar di atas, keliling daerah arsiran}=\:....\\ &\text{a}.\quad 44\:\:\textrm{cm}\\ &\text{b}.\quad 66\:\:\textrm{cm}\\ &\text{c}.\quad 88\:\:\textrm{cm}\\ &\text{d}.\quad 132\:\:\textrm{cm}\\\\ &\textrm{Jawab}:\quad \textbf{c}\\ &\begin{aligned}K&=\displaystyle \frac{1}{2}\textrm{lingkaran besar}+\textrm{1 lingkaran kecil penuh}\\ &=\displaystyle \frac{1}{2}\pi d_{\textrm{besar}}+\pi d_{\textrm{kecil}}\\ &=\displaystyle \frac{1}{2}\frac{22}{7}.28+\displaystyle \frac{22}{7}.14\\ &=44+44\\ &=88\:\: \textrm{cm}\end{aligned}\end{aligned}$.
$\begin{aligned}13.\quad&\textrm{Perhatikan gambar berikut}\end{aligned}$.
$\begin{aligned}\qquad&\textrm{Berdasarkan gambar di atas, keliling daerah arsiran}=\:....\\ &\text{a}.\quad 31,4\:\:\textrm{cm}\\ &\text{b}.\quad 62,8\:\:\textrm{cm}\\ &\text{c}.\quad 94,2\:\:\textrm{cm}\\ &\text{d}.\quad 125,6\:\:\textrm{cm}\\\\ &\textrm{Jawab}:\quad \textbf{d}\\ &\begin{aligned}K&=2\:\textrm{lingkaran besar}\\ &=2\pi d\\ &=2(3,14).20\\ &=125,6\:\: \textrm{cm}\end{aligned}\end{aligned}$.
$\begin{aligned}14.\quad&\textrm{Perhatikan gambar berikut}\end{aligned}$.
$\begin{aligned}\qquad&\textrm{Berdasarkan gambar di atas, besar keliling daerah}\\ &\textrm{jika diketahui jari-jari lingkarannyanya 10 cm }\\ &\textrm{adalah}\: .... \\ &\text{a}.\quad 82,8\:\:\textrm{cm}\\ &\text{b}.\quad 67,1\:\:\textrm{cm}\\ &\text{c}.\quad 61,1\:\:\textrm{cm}\\ &\text{d}.\quad 47,1\:\:\textrm{cm}\\\\ &\textrm{Jawab}:\quad \textbf{b}\\ &\begin{aligned}K&=\displaystyle \frac{3}{4}\:\textrm{lingkaran}+2r\\ &=\displaystyle \frac{3}{4}(2\pi r)+2r\\ &=\displaystyle \frac{3}{4}.2.(3,14).10+20\\ &=47,1+20\\ &=67,1\:\: \textrm{cm}\end{aligned}\end{aligned}$.
$\begin{aligned}15.\quad&\textrm{Perhatikan gambar berikut}\end{aligned}$.
$\begin{aligned}\qquad&\textrm{Berdasarkan gambar di atas, keliling daerah arsiran}=\: .... \\ &\text{a}.\quad 55\:\:\textrm{cm}\\ &\text{b}.\quad 62\:\:\textrm{cm}\\ &\text{c}.\quad 69\:\:\textrm{cm}\\ &\text{d}.\quad 83\:\:\textrm{cm}\\\\ &\textrm{Jawab}:\quad \textbf{a}\\ &\begin{aligned}K&=\displaystyle \frac{3}{4}\:\textrm{lingkaran}_{\text{kecil}}+\displaystyle \frac{1}{4}\:\textrm{lingkaran}_{\text{besar}}+7+7\\ &=\displaystyle \frac{3}{4}(2\pi r_{\textrm{kecil}})+\displaystyle \frac{1}{4}(2\pi r_{\textrm{besar}})+14\\ &=\displaystyle \frac{3}{4}.2.\displaystyle \frac{22}{7}.7+\displaystyle \frac{1}{4}.2.\displaystyle \frac{22}{7}.14\\ &=\displaystyle \frac{5}{4}.2.\displaystyle \frac{22}{7}.7\\ &=55\:\: \textrm{cm}\end{aligned}\end{aligned}$.
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