Answer:
If the spool has 10 cm of circumference or perimeter, this means that 10 cm of thread fits the whole circumference of the spool, which also means that
1 unwind is equivalent to 10 cm of thread.
Then, we have to make the following question:
If 10 cm of thread is equivalent to 1 unwind, to how many unwinds is equivalent 80 cm of thread?
If we want to know how many time does Alex need to unwind the spool, we can use the following relation also called the Rule of Three:
[tex]10 cm----1 unwind[/tex]
[tex]80 cm----X unwinds[/tex]
[tex]X=\frac{80cm(1unwind)}{10cm}[/tex]
[tex]X=8unwinds[/tex]
The answer is:
Alex must unwind the spool 8 times in order to get [tex]80[/tex] cm of thread
