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Mathematics 2 Ms. Meek Missing Number Problems Review

Mathematics 2 Ms. Meek Missing Number Problems Review. Review: Addition With Missing Numbers. An addition problem has at least two addends and a sum.

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Mathematics 2 Ms. Meek Missing Number Problems Review

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  1. Mathematics 2Ms. Meek Missing Number Problems Review

  2. Review: Addition With Missing Numbers An addition problem has at least two addends and a sum. We have already learned how to solve for a sum however, if we know one addend, and we know the sum, we can also learn to solve for the other addend.

  3. Addition With Missing Numbers Often times, when we are given a problem with a missing addend, there is something called a variable put in the place of that missing number. A variable represents a missing number. Example: 12 + X = 20  variable

  4. Solving for the Missing Number Example: 12 + X = 20  Variable How do we find the missing number? We work backward. We use subtraction to find the missing number.

  5. Solving for the Missing Number Example: 12 + X = 20  Variable Take the answer and subtract what we know to solve for the missing number. 20 – 12 = 8 Plug this answer into the original problem to check it. 12 + 8 = 20

  6. Review: Solving a Word Problem When solving a word problem, there are several steps: • Read the problem carefully. • Underline important words that help to indicate what operation should be used. • Identify and write out the numbers needed to solve the problem. • Use pencil and paper to work out the answer.

  7. Missing Addend Word Problem Today we will practice solving word problems in which the total, or sum is given and an addend is missing. We can solve these just like problems that have a missing addend, we subtract to find the missing number.

  8. Missing Addend Word Problem Example 1: Walter had 8 marbles. Then Lamont gave him some more marbles. Walter has 17 marbles now. How many marbles did Lamont give him? If we can recognize the plot, we can write a number sentence to solve the problem.

  9. Missing Addend Word Problem • We know Walter had some marbles, then he received some more. • This problem has a “some and some more” plot so it can be represented with an addition formula. • We know the “some” number and we know the total number. So, we put these numbers into the same formula. Formula: Some + Some more = Total Problem: 8 + x marbles = 17 marbles

  10. Missing addend Word Problem Formula: Some + Some more = Total Problem: 8 + x marbles = 17 marbles We see that one of the addends is missing. One way to find the missing number is to ask an addition question. “Eight plus what number equals seventeen?” 8 + m = 17 Since 8 + 9 = 17, we know that Lamont gave Walter 9 marbles.

  11. Missing addend Word Problem Formula: Some + Some more = Total Problem: 8 + x marbles = 17 marbles We can also solve by asking a subtraction question. “ 17 minus 8 equals what?” Since 17 – 8 = 9, we know that Lamont gave Walter 9 marbles.

  12. Missing addend Word Problem To check the answer, we plug in the number to see if it correctly completes the problem. Walter had 8 marbles. Then Lamont gave him 9 marbles. Walter now has 17 marbles.

  13. Missing addend Word Problem Some addition problems are about parts adding up to a whole. Formula: Part + Part = Whole Example 2: There are 24 students in the whole class. If there are 14 boys in the class, how many girls are there?

  14. Missing addend Word Problem Example 2: There are 24 students in the whole class. If there are 14 boys in the class, how many girls are there? One part of the class is boys and other part is girls. Formula: Part + Part = Whole Problem: 14 boys + x girls = 24 students

  15. Missing addend Word Problem Formula: Part + Part = Whole Problem: 14 boys + x girls = 24 students We can write the number sentence 14 + g = 24 Since 14 + 10 = 24, we know that there are 10 girls in the class.

  16. Review:Subtraction With Missing Numbers A subtraction problem has at least two number amounts, the smaller amount is taken away from the larger amount, and a difference. If we know one number, and we know the difference, we can also learn to solve forthe other number.

  17. Subtraction With Missing Numbers Often times, when we are given a problem with a missing number, there is something called a variable put in the place of that missing number. A variable represents a missing number. Example: 14 - X = 6  variable

  18. Solving for the Missing Number Subtract Down Nine minus six Equals three. Add Up Three plus six Equals nine. 9 -6 3 When solving for the missing number, first set the problem up vertically. We “subtract down to find the bottom number and “add up” to find the top number.

  19. Solving for the Missing Number Subtract Down Fourteen minus what number Equals six? Add Up Six plus what number equals fourteen? 14 -n 6 Example: 14 – n = 6

  20. Solving for the Missing Number Subtract Down Fourteen minus what number Equals six? Add Up Six plus what number equals fourteen? 14 -n 6 Often it is easier to find a missing number by “adding up”. If we add 8 to 6 we get 14, so the missing number is 8. We can check our answer by replacing n with 8 in the original problem.

  21. Missing Number Word Problem Today we will practice solving word problems in which the difference is given and one number is missing. We can solve these just like problems that have a missing number, we subtract down if we are missing the bottom number, and add up if we are missing the top number.

  22. Missing Number Word Problem Example: Walter had 8 marbles. Then his brother Lamont lost some of his marbles. Walter now has 3 marbles now. How many marbles did Lamont loose? If we can recognize the plot, we can write a number sentence to solve the problem.

  23. Missing Number Word Problem • We know Walter had some marbles, then some were lost (taken away). • This problem has a “some-some went away” plot so it can be represented with a subtraction formula. • We know the “some” number and we know the difference. So, we put these numbers into the same formula. Formula: Some – Some went away = difference Problem: 8 - x marbles = 3 marbles

  24. Missing addend Word Problem Add Up Three plus what number Equals eight. Subtract Down Eight minus what number Equals three? Formula: Some – Some went away = difference Problem: 8 - xmarbles = 3 marbles To solve, write the problem vertically. 8 -m 3 m = 5 Plug 5 into the problem to check.

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