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If three circular metal discs of equal thickness whose radii are 5cm, 20cm and 40cm are melted down to form one circular disc of the same thickness, find its radius.

Respuesta :

caylus

Answer: 45 (cm)

Step-by-step explanation:

Since the discs have the same thickness, we will think about the areas.

Let say x the new radius:

[tex]\pi*5^2+\pi*20^2+\pi*40^2=\pi*x^2\\\Longrightarrow\ 5^2+20^2+40^2=x^2\\\\\Longrightarrow\ 2025=x^2\\\\\Longrightarrow\ x=\sqrt{2025} =45[/tex]

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