Answer:
C = 4
Step-by-step explanation:
Given : Given a circle with measures of (C, d, and r) and a circle with measures of (C', d', and r').
and 
We have to find the value of C when C' = 16
Consider, The given circle with measures of (C, d, and r) and a circle with measures of (C', d', and r').
Since, Circumference of circle is directly proportional to the diameter of circle.
Thus, C ∝ d
and C' ∝ d'
Given 
Thus, 
Simplify , we have,
C' = 16

Simplify, we get,

Thus, C = 4