Comparative Relational Thinking Subtraction Lets Review Are these

Comparative Relational Thinking Subtraction

Let’s Review Are these equations true or false? 6 7 - 4 - 1= =78 - 5 How do you know the equation is true? FALSE TRUE

Let’s Review Fill in the blank 12 - 3= 1710 __= 5 - 615 =20 n- -__ How did you solve the equation? n 6 2= 9

Let’s Review What strategies do you use to subtract? Count Back Break Apart Friendly Numbers Think addition Add up

Why do Friendly Numbers work? Let’s think about an easy problem. 1 I will use think addition strategy first! 17 = 8 + ___ 2 17 - 8 3 4 5 6 7 8 9 17 - 8 = 9

Why do Friendly Numbers work? +3 = 20 Let’s think about adding the same value. 1 2 3 4 5 6 7 8 I can keep If I move 17 toa 20… constant to keep a difference. of 9… 8 moves to 11 17 - 8 +3 = 11 9 17 - 8 = 9 20 - 11 = 9

Why do Friendly Numbers work? -7 = 10 Let’s try subtracting the same value. 1 2 3 4 5 6 7 8 I can keep If I move 17 toa 10… constant to keep a difference. of 9… 8 moves to 1 17 - 8 -7 = 1 9 17 - 8 = 9 10 - 1 = 9

Think about using Friendly Numbers and a Constant Difference to subtract… +3 = 49 +3 = 30 46 - 27 If I add 3 to 27, IIlike Then subtract 49 I need to add 3 and 30 Ito find then need to subtract with to difference. 27 to make add 3 to 46… 46 multiples of 10, The answer is 19! 30. 49+ -3 so… 30= = 4919

Using Friendly Numbers and a Constant Difference in Comparative Relational Thinking +3 = 70 Let’s determine if this equation is TRUE or FALSE. Using friendly numbers, If you add 3 oftomaking the 18, a but instead you 10, need I would to change add 3 toone the number on 67. one side to match the other side. 67 - 18 = 46 - 21 +3 +3 70 - 21 = 46 - 21 +3 = 21 67 - 18 = 46 - 21 I don’t BOTHwant numbers to solve… do So, I can add 3 to 18 NOT I 67 just match, + 3 want is 70. sotoit is to get 21? COMPARE FALSE!!!

Using Friendly Numbers and a Constant Difference in Comparative Relational Thinking to find an Unknown Find the unknown. 743 - 467 = � - 480 +13 + 13 756 480 The unknown is equal to 756!! First, Then I change I wouldthe addvalue or of subtract one number the same to be value the same to theas other the number on to thekeep other a constant side of the difference. equal sign.

True or False? 937 - 580 = 940 - 583

True or False? 5, 845 - 3, 782 = 5, 832 - 3, 795

Find the missing number. 346 - 287 = n - 250

Find the missing number. 9, 567 - 8, 342 = ___ - 8, 348