Mathematics Lesson Grade 3: Money: Adding Decimals

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Mathematics LessonGrade 3 Money Adding Decimals

• By Mandy Wood

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Lets Learn How to Add Numbers with Decimals

• Now that you know how to add whole numbers,
  learning how to add decimal numbers will be a
  piece of cake! First, we will begin with a review
  of how to add one, two, and three digit numbers.
  Remember the rules for carrying!
• Try this worksheet Review WS

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Great! Now that you have successfully completed
your review sheet, lets move on to adding
decimals.

• What exactly is a decimal you might ask?
• A decimal is a point or period like this .
• It represents a part of a whole number.
• For example, the number 2 is less than the number
  2.2. 2.2 is read two and two tenths. The
  number equals two whole ones, and two tenths of a
  one.

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Hundreds, Tens, Ones, Tenths, Hundredths

• Lets go back to what we know about how numbers
  are categorized. Numbers are divided into ones,
  tens, and hundreds. They are also divided into
  smaller parts. Ten tenths equal a single one.
  One hundred hundredths equal a single one.
  Because numbers go on forever, there can be
  numbers called ten millions or ten-millionths.
  That is a lot of numbers!

The decimal goes here!
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Decimals are Everywhere!

• When do you come in contact with adding decimals?
  Here are some examples
• Money (1.40 0.25 ?)
• Weight ( .2 lbs 1.2 lbs ?)
• Measurements ( 1.1 m .05 m ?)
• Other numbers that represent parts of a whole
  can be written in decimal form. For example,
  half (½) of a pizza can be written .5 because ½
  .5

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Money

• Adding money is a great way to practice adding
  numbers with decimals. First, lets review the
  value of each coin!

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Pennies

• A penny equals 1 cent. We write this as one
  hundredth of a dollar or .01

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Nickels

• A nickel equals 5 cents. We write this as five
  hundredths of a dollar or .05

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Dimes

• A dime equals 10 cents. We write this as one
  tenth of a dollar or .10

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Quarters

• A quarter equals 25 cents. It is ¼ or
  one-quarter of a dollar. We write this as two
  tenths and five hundredths of a dollar or .25

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Dollars

• In our lesson, we will use one, five, and ten
  dollar bills. This is what they look like

5 Bill
1 Bill
10 Bill
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Buy It with the Little Farmer!

• Try this game to practice counting money. You
  will need to know how to count and add the
  correct amount of dollars and change for the
  upcoming activity!
• Buy It with the Little Farmer Game

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Adding Decimals

• Adding decimals is really no different from
  adding whole numbers.
• First, line up the numbers vertically (up and
  down) as you normally do.
• 1
• 21.04 21.04
• 6.78 6.78
• 27 82
• The only thing you have to do differently is to
  position the decimal. Make a straight line down
  that connects the two decimals and the third one
  that will be in the sum.
• Now, add as you normally would! Dont forget to
  add the dollar sign at the front of the sum!
  Great job!

Now Add
Dont forget the dollar sign!
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Activity Time

• For this activity you will need either real or
  play money, or you will need to print off your
  own money online.
• Here is a good website for printing off your own
  sheets of money
• MoneyInstructor.com

Next Page
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Supply Store Activity

• Materials erasers, pencils, pens, notebooks,
  crayons, and other classroom objects
• Have the class create their own supply store.
  The teacher will write the prices of the objects
  on the board. Students will take turns being the
  cashier and the customer. The customer practices
  adding decimal numbers by adding up his or her
  items and paying for them, and the cashiers job
  is to check his or her answer to see if it is
  correct! Students will love this simulation
  because they get to use money to buy and sell! No
  calculators only pencil and paper!

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Closure/Assessment

• After the fun activity, we are going to do a
  worksheet to test our new skills in adding
  decimal numbers! Click below for the worksheet!
• Adding Decimals Worksheet
• Teacher Resource for Teaching Money