Lesson 3: Decimals Flashcards
(2 cards)
A Decimal Is A Kind Of Fraction.
You Will Learn:
*What Is A Decimal?
*What Is A Place Value?
*How Do You Add & Subtract Decimals?
What Is A Decimal
Like The Fractions You Learned About In The Last Lesson, Decimals Are Parts Of One Whole.
Example:
$1 Equals One Dollar, And One Dollar Is 100 Cents. A Dime Is 10 Cents, Or 10/100. When we write it as a fraction.
To Write It As A Decimal, You Use A Point. Decimals Are Shown As Numbers Coming After A Dot Instead Of Numbers Over Denominator The Dot Is Called A Point, And It Looks Just Like A Period At The End Of This Sentence.
*In Decimals, 10 Cents = .10 or .1(Because If The Last Zero Comes After A Point, You Don’t Have To Show It.)
*30 Cents Is Shown As .30 or (.3) And 70 cents Is Shown As .70 or (.7)
*Often In Decimals, You Will See A Zero Before The Point. This Shows Where The Whole Number Would Be: 0.10 or 0.30 or 0.75
Counting In Tens:
Decimals Are Parts Of A Whole That Are Only Counted In Tens & Multiples Of Ten. Multiples Of Ten Means 100, 1000, 10000, 100000 And All The Wat To Billions And Further. The Denominator Will Always Be 10, 100, 1000 etc.
So 0.1 is 1/10 And 0.7 Is 7/10. But What If It Is A Smaller Fraction Of The Whole? If We Only Have One Penny, Then Show 1/100 When We Write As A Fraction. As A Decimal We Write It 0.01 & 0.07 Would Be The Same 7/100.
0.007 Is The Same As 7/1000, So It Is An Even Smaller Part Of The Whole. It Keeps Going. Decimals To The Right Of The Point Get Smaller And Smaller The Furter They Are From The Point. We Move Them To A Different Place After The Point To Show A Different Value.
Place Value
The Position To The Right Of The Point Is Called A Place Value. Whole Numbers On The Left Have Place Values, Too. Whole Numbers Get Bigger & Bigger As They Get Further From The Point.
1,342,365.1427
The Number 6 Is In The Tens Place. The 6 In The Tens Place Has A Value Of 60. 6x10=60. The Hundreds Place Is A 3. That 3 Has A Value Of 300. 3x10=300.
What About The Place Values To The Right Of The Decimal Point?
They Are All Parts Smaller Than 1. The Tenths Place In The Number Above Is A 1. The 1 Is One-Tenth Of A Whole, Or 1/10. The Hundreths Place Is A 4, Which Is Four One-Hundreths, Or 4/100.
Writing Integers As Decimals
Any Integer(Whole Number) Can Be Written As A Decimal.
Example:
The Number 1 Can Be Written As A Decimal(1.0) Or Not A Decimal(1)
You Are Probably Used To Seeing Money Shown This Way. Often $1 Is Written As $1.00. Two Dollars And 25 Cents Is Shown As $2.25, Which Is The Same As 2 And 25/100. So You’ve Been Using Decimals All Along In Everyday Life.
Adding & Subtracting Decimals
Adding Decimals Is Like Adding Whole Numbers. But There Are A Few Important Differences. The Decimal Points Must Be Lined Up When You Are Adding Or Subtracting. You Have To Do This So Everything Stays In The Right Place Value. So Put The Numbers You Are Adding Or Subtracting Under Each Other.
10.80 7.122 10.80 7.122
+5.34 -3.41(WRONG) +5.34= 16.14 -3.410=3.712(RIGHT)
Add The Numbers That Are Right Above & Below Each Other. Start With The Numbers On The Farthest Right Just Like You Do With Whole Numbers. You Can Quickly Add & Subtract Decimals On A Calculator.
Test Tip: Learn To Use A Calculator!
Study Quiz: 100% 3 out of 3 correct
