An introduction to addition final versionPresentation Transcript
An Introduction to Addition Teresita Powell Tec-539 Digital Media in Education Dr. Charles Elliot
Our Goals You will be able to recognize the math symbol that tells you when to combine items into two sets using 1,2, and 3-digit numbers. You will be able to use counting strategies to figure out how many items are in two sets when they are combined. You will be able to represent numbers using objects or pictures to solve addition problems.
What is addition? Addition is a procedure we use to find out how many items we have. Count the apples in the blue box below. How many apples are there in the blue box? Yes there are 2 apples. In math rather than saying, “how many apples are there” we use the addition sign, sometimes people call it the “plus” sign. We also use another sign called the “equal” sign . The equal sign means to write the number to represent the quantity of the items on the left. The number that you write must tell you how many items there are on the left. See the addition and equal sign below. 2 1 apple plus 1 apple equals 2 apples
Let’s Practice How many trees are there? 2 + 1 = 3 3 Yes there are 3 trees! There will not always be pictures to help, but you can create your own pictures to help you add.
A little more practice What did you get? 4 apples 4 flowers 3 ladybugs 5 Soccer balls
Creating your own pictures to help you add. 4 + 2= There are no pictures here to help and it might take a while to draw them all, so you can use dots instead! 4 + 2= . . . . + ..= Count the dots and you will know the answer to 4 plus 2 equals If you said, “6” then you’ve got it!
How do you add larger numbers? 31 + 25= 31 + 25 56 First we line up the numbers to make it easier to manage. This way we can break the problem into smaller pieces, so that we do not have to draw 31 dots plus 56 dots. This would take too much time. Next we add the numbers from right to left. 1 plus 5 equals 6 So we place this number below the one and five. Next we add 3 plus 2, which equals five so we place this number below the three and the two. Our answer is 56!
Every number has a place To understand our next lesson in addition you must know that each number has a place value. Take the number 125 for example. The one is in the hundreds place the 2 is in the tens place and the 5 is in the ones place . Sometimes when we add numbers the total is more than ten. When this happens we must perform a procedure called “carrying” See the example below 1 2 5
How do you add when you have 3 digits? 175 + 204 = 175 + 204 379 First you line up the numbers. Again this breaks the problem into 3 smaller pieces, and makes it easier to manage. Second you add the digits from right to left. Five plus 4 equals 9 ,so you write the 9 below the five and nine. Next 7 plus 0 equals 7, so you write the 7 below the seven and zero. Finally, 1 plus 2 equals 3, so you write the 3 below the one and the one and two!
Adding numbers that equal 2 digit number 789 + 103 = 1 789 + 103 2 1 789 + 103 92 789 + 103 892 First you line up the numbers. Second you add 9 plus 3, which equals 12, so now you must break up the number 12. You do this by placing the 2 under the nine and 3 and carrying the 1 to the second column. The one will be added to eight and zero in the middle column. Your last step is to add 7 plus 1 which equals eight! You place the eight below the seven and the one.