Grade 4 A C Math Strategies to Mentally

Using Mental Math to Add and Subtract Lesson 4 -1 CCSS 4. NBT. 3,

Warm Up Javier buys a box of pudding mix and a box of oatmeal.

Think and Write When are you able to do mental math in your head?

Using Mental Math to Add �What ways could you find the sum of 34

Adding with Mental Math: Method 2 �To add 45 + 37, you could also

Try It! �Use mental math to add. � 36 + 34 � 99 +

Subtracting with Mental Math The problem is 63 – 17. You could first think:

Subtracting Mentally: Method 2 Another way to do 63 – 17 is to change

Try It! �Use mental math to subtract. � 172 – 14 � 260 –

Subtracting Across Zeros Lesson 4 -5 CCSS 4. NBT. 4

Think and Write �You have learned how to subtract when a number has one

Subtracting Across Zero � When you subtract across zero, it is important to regroup

Slides: 13

Download presentation

Grade 4 A. C. Math Strategies to Mentally Add and Subtract Numbers and Subtract Across Zero Power Point

Using Mental Math to Add and Subtract Lesson 4 -1 CCSS 4. NBT. 3, 4. OA. 3

Warm Up Javier buys a box of pudding mix and a box of oatmeal. The mass of the box of pudding mix is 100 grams. If the total mass of both boxes is 550 grams, how much does the box of oatmeal weigh?

Think and Write When are you able to do mental math in your head? When do you need to use paper and pencil to do math?

Using Mental Math to Add �What ways could you find the sum of 34 + 28? • One way is to use mental math. First, break apart each number into tens and ones. 34 turns into 30 + 4, and 28 turns into 20 + 8. Add 30 + 20, which is 50. Then add 4 + 8= 12,

Adding with Mental Math: Method 2 �To add 45 + 37, you could also try only breaking apart one number. You could break 37 into 30 + 7. Then do 45 + 30 which gives you 75, and then add 75 + 7. �Try it with 28 + 46.

Try It! �Use mental math to add. � 36 + 34 � 99 + 15 � 69 + 23 � 51 + 29 � 48 + 32

Subtracting with Mental Math The problem is 63 – 17. You could first think: What number is close to 17 that is easier to subtract? 20 would be easier to subtract, so what do you need to add to 17 to get 20? Write + 3 under 17, then do 63 - 20. You now have 43. Add 3 to 43 to get your actual answer.

Subtracting Mentally: Method 2 Another way to do 63 – 17 is to change both numbers in the same way. Add 3 to 17 to get 20. Then do the same to 63. 63 + 3 = 66. Do 66 – 20. Is it the same as 63 – 17?

Try It! �Use mental math to subtract. � 172 – 14 � 260 – 17 � 142 – 18 � 368 – 29

Subtracting Across Zeros Lesson 4 -5 CCSS 4. NBT. 4

Think and Write �You have learned how to subtract when a number has one zero in it. How do you subtract when there is more than one zero in the greater number?

Subtracting Across Zero � When you subtract across zero, it is important to regroup properly. For example, when doing subtraction across zero, you turn the last zero into a ten, and the others into nines because you are taking from them.