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SUBTRACTION. Using a Number Line to Count on…. Using the Complementary Addition Method. Welcome to the Subtraction Tutorial. Use the links to find out about subtraction. Using a Number Line to Count on….
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SUBTRACTION Using a Number Line to Count on… Using the Complementary Addition Method Welcome to the Subtraction Tutorial. Use the links to find out about subtraction.
Using a Number Line to Count on… Let’s start with a subtraction question and then use the number line to calculate the answer: 87 – 39 We’ll start at 39 and use addition to count up to 87 So, when you add up all the jumps, you find the answer: 87 – 39 = 48 + 40 + 7 + 1 80 87 39 40
Now your turn… Use a number line to count on to find the answers to these subtraction questions: 176 – 83 419 – 261 3952 – 1795 Click the mouse to reveal the answers… = 93 = 158 = 2157
Look at how we can use a written method alongside this number line: 149 - 86 14 ( 100) + 49 ( 149) 63 So the answer to 149 – 86 is 63 Using the Complementary Addition Method At first, we’ll use the number line to support our written method to solve the following subtraction question: What is 149 – 86? +49 +14 86 100 149 Can you see where all the numbers in the written method come from? We’ll explain this more clearly on the next slide…
Let’s look at the written method… First, set out your subtraction question in columns, one underneath the other: 149 - 86 14 ( 100) We have to add 14 onto 86 to take us up to 100. We use the arrow to show this. + 49 ( 149) We have to add 49 onto 100 to take us up to 149. 63 We have to add 14 and 49 to get the final answer
Now your turn… Use the written method to find the answers to these subtraction questions. You may wish to support your calculation with a number line. 127 – 59 439 – 361 3352 – 1527 Click the mouse to reveal the answers… = 68 = 78 = 1825
Look at how we can use a written method alongside this number line: 7.25 - 4.69 0.01 ( 4.70) 0.30 ( 5.0) + 2.25 ( 7.25) 2.56 So the answer to 7.25 – 4.69 is 2.56 Subtracting Decimal Numbers We’ll use the number line and the written method to answer the following subtraction question involving decimal numbers: 7.25 – 4.69 + 2.25 + 0.01 + 0.30 4.69 4.70 5.0 7.25
What a Problem! Can you use a method for subtraction to solve this following word problem? There are 1248 people at the pantomime. 795 are children. How many are adults? Click the mouse to reveal the answer… Answer: There are 453 adults.