all you have to do is add up all the sides and your answer will be 21 cm
x 21
----- = -----
110 100
Cross multiplication:
110 x 21 / 100
= 23.1
About 23 of the pencils are blue.
When you subtract 4 from 8 you get 4 and this when you add 9 your final answer is 13.
Area of a square
A = s^2, where s = length of side
A = (12 mm)^2
A = 144 mm^2
The area if 144 mm^2.