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L 2: Mental Math : Adding

L 2: Mental Math : Adding. At the end of this lesson you will be able to: Improve mental ability to solve a math problem. Identify information needed for the situation, including distinguishing between relevant and irrelevant information.

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L 2: Mental Math : Adding

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  1. L 2: Mental Math: Adding At the end of this lesson you will be able to: Improve mental ability to solve a math problem. Identify information needed for the situation, including distinguishing between relevant and irrelevant information. Learn to compute math mentally to help estimate the amount of construction supplies needed for various jobs, including deck building. Increase estimation skills.

  2. Take out a piece of paper and number it from 1 to 8 and respond to the following questions. • On the American flag, is the top stripe red or white? Red • Which direction (left or right, as you look at it) does Lincoln’s head face on a penny? Right • How many sides are there on a wooden pencil? 6 • On a traffic light, is the red light on the top or the bottom? Top • How many sides are there to a stop sign? 8 • In which of her hands is the Statue of Liberty’s torch? Left • On which side of the sink (as you face it) is the hot water? Left • Which side of a man’s shirt has the button holes (left or right, if you are wearing the shirt?) Left

  3. In your head add the following numbers: 40 + 40 + 6 + 7 • What answer did you get? • 93 • How did you group the numbers? • Remember we can use the associative property and put the two 40s together and to get 80 and put the 7 and 6 together to get 13 before putting them together. In paper it would look like this: • (40 + 40) + (6 + 7) = • (80) + (13) = 93

  4. Everybody try these next problems in your head and write down the answers on a piece of paper. • 25 + 26 • 51 • 75 + 75 • 150 • 54 + 39 • 93

  5. How would you break up the following numbers? Write your answers on a piece of paper • 79 + 29 80 + 30 – 2 ( 8 + 3 = 11 add 0 ) -2= 108 • 156 + 49 • 155 + 50 (1 down, 1 up) then 150+50 = 200 + 5 = 205 • 156 + 153 • 150 + 150 + 6 + 3 = 300 + 9 = 309

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