Page 10Title: UNIT 1: NUMBER SYSTEM

FLUENCY Common Core Standards:• MCC6.NS.3 Fluently add, subtract, multiply, and divide

multi-digit decimals using the standard algorithm for each operation.

Essential Questions:• When I divide one number by another number, do I

always get a quotient smaller than my original number? • Which strategies are helpful when performing

operations on multi-digit decimals?

Page 11TITLE:

RULES FOR OPERATIONS

WITH DECIMALS:

ADDING & SUBTRACTING DECIMALS

1. Write the numbers you want to add or subtract so that the decimal points are in a line. Add zeros if they are needed. (Annex the zero)

2. Estimate the sum or difference so you can check to see if your final answer is reasonable.

3. If subtracting, regroup if necessary. Add or subtract. Compare the result with your estimate.

MULTIPLYING DECIMALS

1. Place the number with the most digits on top.

2. Multiply.3. Count the number of digits behind

the decimal point in each factor. The number of decimal places in the product is the sum of the number of decimal places in the factors. Insert the decimal in the product.

Quick division vocabulary review:

◦ Dividend: the first number in a division problem; the number being divided.◦ Divisor: the second number in a division problem; the number the dividend is divided into.◦ Quotient: the answer in a division problem. Dividend / Divisor = Quotient

DIVIDING DECIMALS1. In division of decimals, look at the divisor and to move the decimal in the divisor to the right the necessary amount of times to make the divisor a whole number (multiplied by a multiple of ten) Ex. 25.2 ÷ 2.32

2.32 x 100 = 232

DIVIDING DECIMALS…

2. Move the decimal point in the dividend the same number of places to the right. (You are multiplying by the same power of ten from step 1.)Ex. 25.2 ÷ 2.32

2.32 = 232 25.2 = 25202520 ÷ 232 =

Another Way…• Think of division as a fraction:25.2 ÷ 2.32 = 25.2 *Now the divisor is your

2.32 denominator*- You still want to make the divisor (den.) a whole

#- In order to make a whole #, you need to figure

out the power of ten to multiply. Count the # of digits after the decimal there are (2 = two zeros after the 1)

25.2 * 100 = 25202,32 * 100 = 232

100 = fancy “1”100

DIVIDING DECIMALS…

3. Bring the decimal point up onto the quotient line so that it lines up with the dividend.4. Divide as you would with whole number division problems.