Answer: 53.4 cm
Step-by-step explanation:
The formula for circumference is C=2πr or C=πd. These equations are the same. Since the problem gives us the diameter, we'll go ahead and use C=πd.
C=(3.14)(17)
C=53.38=53.4 cm
Answer:

Step-by-step explanation:
Attached above
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First lets rearrange the formula to solve for half-life.
The half-life is the time it takes for half of the element to decay.

So now we need to find "r" which is the rate of decay.
If we rearrange formula to solve for r:

Substituting this into equation for half-life, you get: