If you assume doubling the workers will halve the time taken to finish then 12 analysts will take 21 days To finish in 7 days (1/6 of 42 days) you would need 6 x the original number = 36 analysts.
Brook’s Law (see Wikipedia) suggests than adding extra analysts will actually slow the project down! One reason is the extra people tend to get in each others way.
In order to find circumference you use the formula C (circumference)=2(pi)(r) in which r is the radius. In this case, two and 15 are thirty so to find the circumference all you have is the equation 30 times pi centimeters is equal to the Circumference.
