Brief lesson/example of how to solve for area by decomposing new rectangles.

Today I?m going to talk about Finding area by decomposing rectangles.<br>
So in this example, we have a large rectangle with a smaller rectangle cut out of it.<br>
They are asking us to find the area of the shaded figure so I have colored in this part.<br>
This part is not.<br>
So we are only wanting to find the area of this part. <br>
So the good part is that we do know the full size of the rectangle. It?s 9 cm by 7 cm. So if we start out with that shape, we could get that area.<br>
And we take the area, 9x7 equals 63. That is the area of this whole shape. If the shape was still in there, not cut out.<br>
So, I?m going to put 63 here down in my equation.<br>
Alright, so now we have 63 minus something equals the total sq. cm. <br>
So if we had this, and if we had to physically remove the area of this little shape, we will have to find the area of this little shape.<br>
And we figure that out by multiplying the two sides.<br>
3x2 equals 6. So I?m going to put that. <br>
Now that I?ve got 2 values. <br>
So now I?m going to subtract, 63 minus 6. <br>
I?m going to put that on top of each other.<br>
So we barrow. 13 minus 6 is 7. So we bring the 5 down. It?s 57.<br>
So 63 minus 6 is 57 sq. cm. <br>
So the area is 57 sq. cm.<br>
Again, that was Finding area by decomposing rectangles.<br>