Perbandingan jari jari alas dan tinggi kerucut adalah 7:12. Jika volume kerucut 77cm2 , hitunglah panjang jari jari alas dan tinggi nya!

[tex]$\displaystyle{\begin{split}\frac{r}{t}& = \frac7{12} \\ t & = \frac{12}7r \end{split}}[/tex]

[tex]$\displaystyle{\begin{split} V& = 77 \\ \frac13\pi r^2t & = 77 \\ \frac13\cdot\frac{22}7\cdot r^2\cdot\frac{12}7r&=77\\ \frac{22\cdot12}{3\cdot7\cdot7}r^3&=7\cdot11\\ \frac{2\cdot11\cdot3\cdot2\cdot2}{3\cdot7\cdot7}r^3&=7\cdot11\\ \frac{2^3}{7^2}r^3&=7\\ r^3&=7\cdot\frac{7^2}{2^3}\\ r^3&=\frac{7^3}{2^3}\\ r&=\frac72\\ r&=3\frac12\text{ cm} \end{split}}[/tex]

[tex]$\displaystyle{\begin{split} t& = \frac{12}7r \\ & = \frac{12}7\cdot\frac72\\ &= 6\text{ cm} \end{split}}[/tex]