A belt fits tightly around two pulleys of radii 4 cm and 6 cm respectively and the distance between their centers is 20 cm. Find the length of the belt.

I know the answer is 71.62cm from the answer key but I need to know the process to get there.
The picture of the question can be accessed in this link:
Thanks in advance

1 answer

see the related questions below, and use your numbers.