Answer:
13
Step-by-step explanation:
there is a rule that says that if you add any 2 sides, it should be more than the third. 9+21 is greater than 13. 21+13 is greater than 9. 13 is the only number which if you add 9 to it it will be greater than 21. 12 will equal 21, but it still wont work.
hope this helps :))
Answer: 
Step-by-step explanation:
Let be "C" the circumference of the circle (in feet) and "r" the radius of the circle (in feet).
Based on the information provided in the problem, you know that the circumference of the circle is always
as large as its radius.
Notice that this indicates a multiplication. Then, this means that the circumference of the circle is always equal to
by "r".
Based on this, you can write the following formula that expresses the circumference "C" in terms of the radius "r":

Answer:
its simple its C
Step-by-step explanation:
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