Vocabulary
This word means the answer for an addition problem...
Sum
When adding, which place value do we start in?
Ones Place!
Ones Place!
The school library has 2,458 fiction books and 1,736 nonfiction books.
How many books are in the library altogether?
4,194 Books
True or False, estimating is a form of rounding?
True!
This word means the answer for a subtraction problem...
Difference
True or False:
When adding the bigger number must always be on the top and the smaller number must always be on the bottom?
FALSE!
In addition, you can change the order of the numbers and the sum remains the same.
True or False: When subtracting, the bigger number always has to be on top and the smaller number always has to be on the bottom?
TRUE!
If the smaller number were on top, we would be forced to go into negative numbers and regrouping wouldn't be possible!
In 2025, Detroit had a population of 2,485,637 people and Lansing had a population of 1,763,928 people.
How many people lived in both cities all together?
4,249,565 people
Estimate the following to the nearest thousands:
4,582 + 3,859 = ?
4,582 rounds to 5,000
3,859 rounds to 4,000
5,000 + 4,000 = 9,000
This property shows that changing the order of the numbers (or moving the numbers around) when adding does not change the sum.
We also can call these "turn around facts"
a + b = b + a
Commutative Property
Hint: Commute means to move
489,927 + 214,291 = ?
704,218
674,295 - 329,552 =
344,743
A school had 8,425 pencils. After giving some pencils to students, the school had 3,687 pencils left. How many pencils did the school give out?
4,738 pencils
Estimate to the nearest ten thousand:
73,294 - 51,294 = ?
73,294 rounds to 70,000
51,294 rounds to 50,000
70,000 - 50,000 = 20,000
This property shows that adding 0 to any number does not change its value or who it is.
a + 0 = a
0 + b = b
Identity Property
Hint: Identity means who you are.
319,596 + 32,849 =
Hint: Remember to line up your place values!
352,445
1,258,492 - 32,687 = ?
Hint: Remember to line up your place values!
1,225,805
A museum had 5,243,816 visitors last year. This year, 1,876,459 people visited the museum. How many more visitors did the museum have last year than this year?
3,367,357 more visitors
Estimate to the nearest thousand:
4,590 + 2,190 + 4,987 = ?
4,590 rounds to 5,000
2,190 rounds to 2,000
4,987 rounds to 5,000
5,000 + 2,000 + 5,000 = 12,000
This property shows changing the grouping of numbers or associating numbers with each other differently does not change the sum.
(a + b) + c = (c + a) + b
Associative Property
Hint: Associate means to group/hang out with
1,573,205 + 91,495 + 4,395 =
1,669,095
490,002 - 125,943 =
364,059
During our school book fair, students bought 2,485 books on Monday and 1,736 books on Tuesday. On Wednesday, the school returned 925 damaged books.
How many books were left AFTER the damaged books were returned?
3,296 books
What does it mean if an estimate is UNREASONABLE?
Unreasonable means that it does not make sense, cannot be the answer, or that answer is wrong/incorrect.