since pi is irrational and it is used in the formula, we cannot give an exact answer except in terms of pi (we can give an aproxamation using 3.14 =aprox pi, but it is not exact)
ok
circumfernce=2pir
r=15
circumference=2pi15
circumference=30pi
exact=30pi cm
if you want to aprox pi=3.14 then
aprox circumfernce=94.2 cm