To show how an area is made be sure to trace your block exactly, then label the dimensions
4 . 5
X
4.5
Then count the squares to see if your mathematics matches the image. Rember when we multiply decimals if we say what it is orally, then the answer makes more sense. In this case, tenths x tenths = hundredths.
1 2 3 4 .5
5 6 7 8 .5
9 10 11 12 .5
13 14 15 16 .5
.5 .5 .5 .5 .25
..
Use expanded form for easy multiplication.
4 + .5
x 4 + .5
16 + 2 because 4 x 4 = 16 and 4 x .5 =2
2 + .25 because .5 x 4=2 and .5x.5=.25
Total all for 20.25 Does that match the grid?
To find the surface area of a block you have to think about how many rectangles are there in a block. Are all faces congruent?Do some have different dimensions than the other ones? It might help to remember that tops and bottoms match (2x) and sides also match up (4) in rectangular prisms
