The decimal you put would be “two ten-millionths” if read out loud. If the allowable amount is 10 parts per billion, it would be 1 part per 100 million. Because 2 parts per 10 million is also 20 parts per 100 million, it is not not an acceptable amount
To find the formula to find radius, solve for r using the formula for circumference.
to solve:
1. divide each side by 2

2. you get
r = c/2