Respuesta :

Answer:

r = 50

Step-by-step explanation:

We know that:

  • [tex]\frac{C}{C'}=5[/tex]
  • [tex]d'=20[/tex]

So, the ratio between the circumferences is 4 and the diameter of the second circle is 20. In this case, we have to use the ratio between those two circumferences, because that's what is our given data.

[tex]\frac{C}{C'}=\frac{d}{d'}\\5=\frac{d}{20}\\ 100=d[/tex]

From this proportion, we deduct that the diameter of the initial circle is 100. Now, we know that the radius in a circumference is have the diameter. Therefore, the radius is:

[tex]r=\frac{d}{2}=\frac{100}{2}=50[/tex]

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