Answer:
C≈6.28mm
Step-by-step explanation:
C=2πr
= 2·π·1≈6.28319mm
B. is the answer hope I got it right: )
Yesterday's price of notebook = $3.45
Today's price of notebook = $3.20
We have to determine the percentage decrease in the cost of notebook.
Percentage decrease = (Decrease
Old price) 
So, percentage decrease = 
=
= 7.246%
= 7.25%
Therefore, there is 7.25% of decrease in the cost of the notebook.