The cone

The cone with a base radius of 12 cm and a height of 20 cm was truncated at a distance of 6 cm from the base, thus creating a truncated cone. Find the radius of the base of the truncated cone.

Correct answer:

r₂ =  8.4 cm

Step-by-step explanation:

$$\begin{gathered} r_1=12\text{ cm } \\ h=20\text{ cm } \\ {h}_2=6\text{ cm } \\ {r}_1:h=r_2:(h-h_2) \\ {r}_2=r_1\cdot {\displaystyle \frac{h-h_2}{h}}=12\cdot {\displaystyle \frac{20-6}{20}}={\displaystyle \frac{42}{5}}\text{ cm}=8.4\text{ cm} \end{gathered}$$

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