<PRE><B>Question 846022</B>
You need to find the circumference of the drum . The length is not important.
2 pi r=C
r=d/2
2 pi.4=C
.8pi=C

16*8/10*pi=40.2 meters of rope
See also 
http://www.algebra.com/algebra/homework/Pythagorean-theorem/Pythagorean-theorem.faq.question.846011.html
</PRE>