Module 4 Lesson 4

Add and subtract multiples of 10 and some ones within 100. Objective Add and subtract multiples of 10 and some ones within 100.

174 258 734 860 902 Place Value Say the number. What digit is in the tens place? What’s the value of the 7? State the value of the 1. State the place of the 4. Let’s try some more by asking the same questions. 174 258 734 860 902

Making a Ten Drill 4 3 7 17 13 23 27 42 48 58 7 + ___ = 10 Let’s find missing parts to make ten. If I say 7, you would say 3. Ready? 7. Say the number sentence. Let’s try some more numbers: 4 3 7 17 13 23 27 42 48 58

Making the Next Ten to Add When I say, 9+4, you say 10+3. Ready? 9+4. What’s the answer? Let’s try some others: 19+4 9+6 8+3 8+5 7+6 7+4 29+4 19+6 18+3 18+5 17+6 17+4 49+4 29+6 48+3 88+5 27+6 67+4 79+4 59+6

Concept Development There are 5 yellow cubes. How many linking cubes am I showing in this stick? How many in this stick? What is the difference between 8 and 5? What number sentence could I use to represent the difference between 8 and 5? 8–5=3.

Concept Development Continued Has the difference changed? But what new number sentence can I use to represent the difference between my two sticks? 9–6=3. Is the difference still 3? YES!

Concept Development Continued If I add more to each bar. Did the difference change? Let’s test this idea. When we add the same amount to each number in a subtraction sentence, the difference stays the same. Now let’s try this with a new problem. 34 – 28 Now that is challenging! Try this one: 36 – 30. How did you know the answer so fast? Yes! Is it easier to subtract just tens!

Concept Development Continued Now, can you tell me how 34 – 28 and my other problem, 36 – 30, are related? Turn and talk. Now how long is each bar? We added 2 to each bar to make the problem easy! Now it’s your turn. On your white board, solve these problems by making a tape diagram. Add on to both numbers to make the problem easier. 22-8 26-19 33-18

Concept Development Continued There are 6 red cubes on one end and 4 red on the other end. How many yellows are in the middle? What is the total number of cubes? Let’s make 2 different addition sentences. What is the addition sentence for the total number of cubes? Now instead let’s join the 1 yellow with the 6 red. How do you know this is true 6+5 = 7+4?

Concept Development Continued Let’s use that same idea with larger numbers to make tens. Let’s solve 28 + 36. What does 28 need to be the next ten? What is 2 less than 36? How do you know this is true: 28+36=30+34? We can also show 2 more for 28 with our number bond. Let’s write both models in our journals and explain them to your partner.

Concept Development Continued Let’s do some more practice with the following problems: 19+35 36+29 78+24 37+46

Story Problem Carlos bought 61 t-shirts. He gave 29 of them to his friends. How many t-shirts does Carlos have left? Solve! Share!