Alex needs to unwind the spool 8 times to get the 80 cm of thread he needs.
Here's how we can figure it out:
Calculate the length of thread on one unwind:
Since the circumference of the spool is 10 cm, the radius is 5 cm (circumference = 2 * pi * radius).
Therefore, the length of thread on one unwind is equal to the circumference, which is 10 cm.
Divide the total thread needed by the length per unwind:
Alex needs 80 cm of thread, and each unwind provides 10 cm.
So, we need to divide: 80 cm / 10 cm/unwind = 8 unwinds.
Therefore, Alex needs to unwind the spool 8 times to get the 80 cm of thread he needs.
Question
Alex needs 80 cm of thread for a sewing project. The thread is on a spool with a circumference of 10 cm. How many times must alex unwind the spool to get the length f the thread he needs?