Question

Given a circle with measures of (C, d, and r) and a circle with measures of (C', d', and r'), what is r if C C' = 5 and d' = 20?

Answer 1

Answer:

r = 50

Step-by-step explanation:

We know that:

• $\frac{C}{C'}=5$
• $d'=20$

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.

$\frac{C}{C'}=\frac{d}{d'}\\5=\frac{d}{20}\\ 100=d$

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:

$r=\frac{d}{2}=\frac{100}{2}=50$