Step-by-step explanation:
the formula to calculate a circumference is
[tex]x \times \pi[/tex]
(consider x as the diameter)
so I'll be noting the circumference as C alongside the circle's ranking
a.
[tex]ca = 6 \times 22 \div 7 \\ = 44 \div 7[/tex]
b.
[tex]cb = 7 \times 22 \div 7 \\ = 154 \div 7 \\ = 22[/tex]
c.
[tex]cc \: = 4 \times 22 \div 7 \\ = 88 \div 7 [/tex]
hope I helped
