Question 265570
Hello, 
Once we get what this (%) symbol means then it might help. To understand it let's use an example: 50% is also written as .50 or .5 or 1/2, the key here is when the %sign is taken away the decimal point is moved to the left two places. (75% is .75)
For the problem we would multiply 2% times 40 or rewritten as:
.02*40 = .8 cm 
This is how much it will increase so the length will be:
40.8 cm 
Make sense?
RJ
A new book I wrote might help you:
www.math-unlock.com