MENTAL MATHS – ADDITION
25 + 10
35
40 – 15
25
Round 26 to the nearest ten.
30
Estimate: 23 + 47 (round to nearest 10 first)
20 + 50 = 70
Name the property:
6 + 4 = 4 + 6
Commutative Property
48 + 32
80
90 – 35
55
Round 143 to the nearest ten.
140
Estimate: 146 + 321 (round to nearest 10)
150 + 320 = 470
Name the property:
(2 + 3) + 5 = 2 + (3 + 5)
Associative Property
125 + 200
325
500 – 275
225
Round 548 to the nearest hundred.
500
Estimate: 198 – 63 (round to nearest 10)
200 – 60 = 140
True or False:
The commutative property works for subtraction.
False
375 + 225
600
620 – 480
140
Round 1,267 to the nearest hundred.
1,300
Estimate: 453 + 287 (round to nearest 100)
500 + 300 = 800
Fill in the blank:
The associative property lets us change the __________ in which we group numbers.
Grouping
468 + 527
995
905 – 478
427
Round 7,849 to the nearest thousand.
8,000
Estimate: 864 – 429 (round to nearest 100)
900 – 400 = 500
Use the associative property to simplify:
(8 + 12) + 20
8 + (12 + 20) = 8 + 32 = 40