Decimals and Decimal Computations

10 x 10 Model

• Square is seen as a whole.

• How many squares make up the whole?

• How many squares are in a half?

• How many squares are in a quarter?

Fraction -Decimal Connection

• Cover up 35/100 of the square

• What is another way to record this part of the whole?

• What is another way to write 1.68?

Familiar Fractions

• 1/4 = what as a decimal?

• 1/5 = What as a decimal?

• 1/20 = what as a decimal?

• 1/8 = what as a decimal?

• What strategy do we use to solve?

Not so Familiar?

• 1/3 = what as a decimal?

• 1/6 = what as a decimal?

• What strategy do we use now?

Estimation = Benchmarking

• Which Fraction would be the approximate of .52

• 1/50

• 1/5

• 1/4

• 1/2

Fraction - Decimal Match

• 2.804, 2.41, 2.6271, 2.211

• 11/5, 2 7/8, 2 5/8, 2 1/3

Comparing Decimals/Fractions

• Estimate using a number line with benchmarks 0 , 1/2 , and 1

• 3/8, 2.567, 5/3, 1 4/5, 1.8765

Computations With Decimals

• What comes to mind when you see these computations?

• 4.907 + 123.01 + 56.1234

• 459.8 + 12.345

• 24.67 + 1.84

• 514.67 / 3.59

Estimation First

• 73.46 + 6.2 + 0.582

• Estimate first

• What is the answer?

• How can you add and subtract decimal numbers that will work every time?

Multiplication

• What is 24 x 63

• So what is

• .24 x 6.3

• 24 x .63

• 2.4 x 63

Division

• 146 / 7 = 20857 (without the decimal point)

• So what is the answer:

• 146 / 0.7

• 1.46 / 7

• 14.6 / 0.7