Chapter 2- Decimals
What will be covered? Place Value Chart Comparing Decimals
Rounding Decimals Add and Subtract Decimals Multiply and Divide Decimals Order of Operations with Decimals Fraction to Decimal
Place Value Chart
Comparing Decimals Line up the decimals vertically.
Start at the left and compare corresponding digits. If the digits are the same, move one place to the right. When two digits are different, the larger number is the one with the larger value.
Example: Comparing Decimals
List from Smallest to Largest 1.834, 1.83, 1.381, 1.38, 1.8 Answer: 1.38, 1.381, 1.8, 1.83, 1.834 1.834 1.83 1.381 1.38 1.8 00
Example 2: Compare Decimals
List from smallest to largest 15.002, 15.02, , , Answer: 15.002 15.02 15.001 15.018 15.001, , 15.002, 15.018, 15.02 0 0
Rounding Decimals Circle the digit value to round to, and draw an arrow to the number to the right If the value is 5 or greater, round the digit value up one If the value is less than 5, drop the values to right of digit
Example: Rounding Decimal
Round to the nearest hundredths 5 or Greater? No Then drop values 137.89 Round to the nearest thousandth 0.39
Examples: More on rounding
Round to the nearest whole number. This is the same thing as rounding to the nearest ones place. 9.0 or 9 or 495
Adding and Subtracting Decimals
Write the numbers to be added vertically and line up the decimal points. Extra zeros may be placed to the right of the decimal points if needed. Add or subtract all the digits with the same place value, starting with the right column and moving to the left. Place the decimal point of the sum or difference in line with the decimal points of the numbers added.
Examples on Adding Decimals
= 3.1 2.16 + 5.26
Example: Adding Decimals
Step 1 Step 2 Step 3 15.3
Example: Subtracting Decimals
Step 1 Step 2 Step 3 15.87 15.870 15.870 1.649 14.221
Multiplying Decimals Steps
Set up in multiplying form – don’t worry about lining up decimals or trailing zeros Multiply Count decimals places in both multiplied numbers Move decimal point in final answer
Example: Multiplying Decimals
Multiply 21.7 x .23 Step 3 Step 1 Step 2 3 Decimal Places 4.991 21.7 X .23 21.7 X .23 651 +4340 4991
More Examples on Multiplication
Step 1 Step 2 Step 3 5.261 45 26305 210440 236745 5.261 45 x x +
Dividing a Decimal by a Whole Number
Set up the division problem Place the decimal point for the quotient directly above the decimal point in the dividend. Then, divide if the numbers were whole numbers. Validate by multiplication.
Dividing by a Whole Number
The decimal points are aligned, one above the other. 2.16 . 16 12 8 48 Divide as you normally divide whole numbers.
Dividing by a Decimal When dividing a decimal by another decimal, the division problem is converted into an equivalent problem that has a whole number as a divisor. Dividing by a Decimal Make the divisor a whole number by moving the decimal point to the right. Mark that position with a caret (). Count the number of places the decimal point moved. Move the decimal point in the dividend to the right the same number of places. Mark that position with a caret. Place the decimal point of your answer directly above the caret marking the point of the dividend. Divide as with whole numbers.
Dividing by a Decimal 2.3 366 549 Example: Divide 4.209 ÷ 1.83. . . .
Move each decimal point to the right two places. . . Place the decimal point of the answer directly above the caret. 2.3 . Mark the new position by a caret (). 366 549 Divide as normal.
Dividing by a Whole Number
Example: Divide ÷ 7 and round to the nearest hundredths. 37.688 Carry out the division to the thousandths place, and then round. An extra zero was added to carry out the division to the required place. 21 53 49 48 42 62 56 60 is rounded to (the nearest hundredths). Note that the remainder is not zero.
Order of Operations 0.3 x 0.5 + ( 0.4x 0.4x 0.4) – 0.036
– 0.036 0.150 0.150 0.214 -0.036 Validate 0.036 0.178 0.214 0.178 0.214
Fraction to Decimal
Fraction to Decimal Validation:
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