Answer:
d = 6 units
Explanation:
Circumference of the circle is given by:
![C = \pi d](https://img.qammunity.org/2020/formulas/mathematics/middle-school/9u5kd44hg7dt04wuyu1gi3g4j0o7aunwou.png)
where, d is the diameter of the circle.
As per the statement:
Given a circle 1 with measures of (C, d, and r) and a circle 2 with measures of (C', d', and r').
Circumference of a circle(C) 1 with diameter(d) is given by:
.....[1]
Also, the circumference of a circle (C') 2 with diameter(d') is given as:
Divide equation [1] and [2] we have;
![(C)/(C') = (\pi d)/(\pi d')](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6i6pzdx1sqwk4zma22t8l8nczgl43xy3fx.png)
⇒
![(C)/(C') = (d)/(d')](https://img.qammunity.org/2020/formulas/mathematics/middle-school/80xxg4k57ltabrczbt0pl0dbdgbhg8dw27.png)
Substitute the given values
and d' = 0.50 then;
![12 = (d)/(0.50)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/belg18x0v0xa2z8sxasf62ie83esvod811.png)
Multiply both sides by 0.50 we have;
6 = d
or
d = 6 units
Therefore, the value of d is, 6 units