CHALLENGING MENTAL ADDITION
125 + 178
303
250 – 127
123
Round 77 to the nearest ten.
80
Estimate: 38 + 62 (round to nearest ten).
40 + 60 = 100
Which property?
9 + 3 = 3 + 9
Commutative Property
689 + 432
1,121
900 – 468
432
Round 6,742 to the nearest thousand.
7,000
Estimate: 784 + 329 (round to nearest hundred).
800 + 300 = 1,100
True or False:
Changing the order of addends changes the total.
False
1,345 + 2,468
3,813
1,560 – 789
771
Round 52,481 to the nearest thousand.
52,000
Estimate: 1,296 – 587 (round to nearest hundred).
1,300 – 600 = 700
Fill in the blank:
The commutative property lets us change the __________ of numbers.
Order
468 + 257
725
640 – 289
351
Round 1,249 to the nearest hundred.
1,200
Estimate: 429 – 167 (round to nearest ten).
430 – 170 = 260
Which property?
(4 + 6) + 10 = 4 + (6 + 10)
Associative Property
2,508 + 3,497
6,005
4,203 – 2,679
1,524
Round 345,678 to the nearest ten thousand.
350,000
Estimate: 4,587 + 3,286 (round to nearest thousand).
5,000 + 3,000 = 8,000
Use the associative property to simplify:
(15 + 25) + 35
15 + (25 + 35) = 15 + 60 = 75