how do we find the area of a circle?

The area of a circle is the number of square units inside that circle. 

where a is the area and r is the radius of the circle.

Example 1:	The radius of a circle is 3 inches.
Solution:
	= 3.14 · (3 in) · (3 in)
	= 3.14 · (9 in2)
	= 28.26 in2

how do we identify soilds?

Solids have special things about them that is identified
they must have :
surface area
volume.

but there are two types of solids:
polyhedra
non-polyhedra

Polyhedra as in saying they must have flat surfaces like these:

Non Polyhedra solids are like these:

how do we calculate the area of a rectangle and a triangle?

To find the area of a triangle, multiply the base by the height, and then multiply by 1/2
     lets say the height is 8 and the base is 6.
1.6x8= 48  
2. 48 x 1/2 = 24.
and thats your area of a triangle.


To find the area of a rectangle , just multiply the width and the height.
for example  w= 15 and h=10  .  15 x 10= 150  and thats the area of a rectangle.