Rounding
Round 172 to the nearest hundred.
Round 172 to the nearest hundred.
172 --> 200
Kate used mental math to add 462 + 323.
How would you break apart these numbers into hundreds, tens and ones?
Kate used mental math to add 462 + 323.
How would you break apart these numbers into hundreds, tens and ones?
400 + 60 + 2
300 + 20 + 3
40 + 30 = 30 + 40
What property of addition is shown above?
A) Associative
B) Identity
C) Commutative
40 + 30 = 30 + 40
What property of addition is shown above?
A) Associative
B) Identity
C) Commutative **
What is the inverse operation of subtraction?
What is the inverse operation of subtraction?
Addition
What is the commutative property of addition?
What is the commutative property of addition?
The commutative property of addition -
when two numbers are added, the sum is the same even if you switch the order of the numbers being added
Round 155 to the nearest ten.
155 --> 150
Add 663 + 202 mentally. What should you add or subtract first to find the sum?
Add 663 + 202 mentally. What should you add or subtract first to find the sum?
- First subtract 202 - 2 = 200
663 - 200 = 463.
463 - 2 = 461.
Show an example of the Identity Property of Addition.
Show an example of the Identity Property of Addition.
Example:
0 + 42 = 42
Michael says 342 - 102 = 240. Check his work using inverse operations. Is he correct?
Michael says 342 - 102 = 240. Check his work using inverse operations. Is he correct?
Yes he is correct because 240 + 102 = 342
Subtract 362 - 171 by using a number line and counting on from 171.
<------------------------------------------------->
171 362
191 is the answer
Estimate the sum of 157 and 172 by rounding to the nearest hundred. Explain your estimate
200 + 200 = 400; I rounded 157 to 200 and 172 to 200.
Use mental math to find 448 -250.
Use mental math to find 448 -250.
250 - 2 = 248
448 - 248 = 200
200 - 2 = 198
Select all of the equations that are true.
1.) 630 + 0 = 0
2) 200 + 270 = 270 + 200
3) 0 + 52 = 52
4) (100 + 0) + 140 = 110 + (0 + 140)
5) 46 + (3 + 440) = (46 + 3) + 440
Select all of the equations that are true.
* #2, 3 and 5 are correct.***
1.) 630 + 0 = 0
2) 200 + 270 = 270 + 200
3) 0 + 52 = 52
4) (100 + 0) + 140 = 110 + (0 + 140)
5) 46 + (3 + 440) = (46 + 3) + 440
Fill in the blank and check your answer using inverse operations.
_______ + 40 = 353
Fill in the blank and check your answer using inverse operations.
_313_ + 40 = 353
Inverse --> 353 - 40 = 313
Stacy thinks she needs $387 for art supplies. She knows she is very close, but is not sure if this is the exact amount she will need. Estimate to find the amount of money Stacy should bring to the store. Explain.
Stacy thinks she needs $387 for art supplies. She knows she is very close, but is not sure if this is the exact amount she will need. Estimate to find the amount of money Stacy should bring to the store.
Round 397 to 390 or 400. You would not want to use compatible numbers to solve this because you might estimate a number lower than 387 (for example: 385) and Stacy won't have enough money.
Estimate the sum of 442, 157 and 123 by rounding to the nearest ten.
Estimate the sum of 442, 157 and 123 by rounding to the nearest ten.
440 + 160 + 120 = 720
Subtract 783 - 103 mentally. First subtract 3 from 103 to get 100. What should the next step be? What is the difference?
A) Add 3 to 783. The difference is 686.
B) Add 100 to 783. The difference is 783.
c) Subtract 3 from 783. The difference is 680
d) Subtract 3 from 783. The difference is 600.
.
Subtract 783 - 103 mentally. First subtract 3 from 103 to get 100. What should the next step be? What is the difference?
Subtract 3 from 783. The difference is 680
(If you do this, it's easy to subtract mentally. 780 - 100 = 680) You can check this by inverse operations. 680 + 103 = 783 so this is correct.
Show an example of the Associative Property of addition with 3 numbers on each side of an equal sign.
Show an example of the Associative Property of addition with 3 different numbers.
Example:
(42 + 9) + 3 = 42 + (9 + 3)
Fill in the blank. Check your answer with the inverse operation.
________ - 40 = 290
Fill in the blank. Check your answer with the inverse operation.
__330___ - 40 = 290
Inverse --> 290 + 40 = 330
Estimate the sum of 243 + 221 using compatible numbers.
Estimate 243 + 221 using compatible numbers.
240 + 220 =460
Estimate the difference of 725 and 113 by rounding to the nearest ten. Explain your estimate.
Find the exact answer of 725 - 113. What is the difference between the exact answer and the estimate?
Estimate the difference of 725 and 113 by rounding to the nearest ten. Explain your estimate.
Find the exact answer of 725 - 113. What is the difference between the exact answer and the estimate?
730 - 120 = 610 (rounding to the tens)
612 - 610 = 2
Add 173 + 104. mentally. Which of the following should you do first to find the sum?
𝖠 Add 4 to 173 and add 4 to 104.
𝖡 Subtract 4 from 173 and add 4 to 104.
𝖢 Add 4 to 173 and subtract 4 from 104.
𝖣 Subtract 4 from 173 and subtract 4 from 104
Add 173 + 104. mentally. Which of the following should you do first to find the sum?
𝖠 Add 4 to 173 and add 4 to 104.
𝖡 Subtract 4 from 173 and add 4 to 104.
𝖢 Add 4 to 173 and subtract 4 from 104. **
𝖣 Subtract 4 from 173 and subtract 4 from 104
Jane recycled 32 cans on Monday and 46 cans on Tuesday. On Wednesday she recycled 22 cans. What is the difference between the amount of cans she recycled on Monday and Tuesday and the amount on Wednesday?
Jane says you can use the Associative Property of subtraction to help you solve this problem? Is she correct? Why or why not?
Jane recycled 32 cans on Monday and 46 cans on Tuesday. On Wednesday she recycled 22 cans. What is the difference between the amount of cans she recycled on Monday and Tuesday and the amount on Wednesday?
Jane says you can use the Associative Property of subtraction to help you solve this problem? Is she correct? Why or why not?
78 - 22 = 56
No, the associative (grouping) property does not work with subtraction because you cannot change the order of numbers and get the same answer.
Sarah says 330 - 440 = 110 because 330 + 110 = 440. Is she correct? Explain.
Sarah says 330 - 440 = 110 because 330 + 110 = 440. Is she correct? Explain.
No, she is not correct because you cannot take a bigger number away from a smaller number. 440 - 330 = 110 would be correct.
Look at the 3s column and row on an addition table. Look at the addends. What pattern do you see? Explain why this pattern is always true. (What property is this pattern showing?)
Look at the 3s column and row on an addition table. Look at the addends. What pattern do you see? Explain why this pattern is always true.
The same sums are in the 3s row and column. This is because the sum of any two numbers is the same no matter which number comes first. This is known as the Commutative Property.