Truncated cone 5

The height of a cone is 7 cm, the length of a side is 10 cm, and the lower radius is 3cm. What could be the possible answer for the upper radius of a truncated cone?

Correct answer:

r₁ =  10.1414 cm

Step-by-step explanation:

$$\begin{gathered} h=7\text{cm} \\ s=10\text{cm} \\ {r}_2=3\text{cm} \\ x=\sqrt{s^2-h^2}=\sqrt{10^2-7^2}=\sqrt{51}\text{cm}\doteq 7.1414\text{cm} \\ r=r_2-x<0 \\ {r}_1=r_2+x=3+7.1414=10.1414\text{cm} \end{gathered}$$

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