Estimation
Multiplication
+/-Decimals
In/Out
100
Write the number closest to the sum: 354 + 222 400 500 600 700 Write a number model for the estimate above
Number closest to the sum: 600 Number model estimate: 400 + 200 = 600
100
2 x 58
116
100
9.6 + 7.3
16.9
100
Rule: Multiply by 5: In Out 5 50 300 3000
In Out 25 250 60 600
200
Write the number closest to the sum: 147 + 823 800 900 1,000 1,200 Write a number model for the estimate above
Number closest to the sum: 900 Number model estimate: 100 + 800 = 900
200
9 x 24
216
200
2.63 + 4.15
6.78
200
Rule: Multiply by 30 In Out 6 20 1500 2700
In Out 180 600 50 90
300
Write the number closest to the sum: 563 + 934 + 718 2,100 2,200 2,300 2,400 Write a number model for the estimate above
Number closest to the sum: 2,200 Number model estimate: 600 + 900 + 700 = 2,200
300
3 x 987
2961
300
8.9 - 5.3
3.6
300
Rule:_______ In Out 6 4200 8 5600 10 5
Rule: * 70 In Out 6 4200 8 5600 10 700 5 350
400
Write the number closest to the sum: 985 + 727 + 115 1,500 1,700 1,800 2,000 Write a number model for the estimate above
Number closest to the sum: 1,800 Number model estimate: 1,000 + 700 + 100 = 1,800
400
67 x 45
3015
400
12.86 - 9.34
3.52
400
Rule:_______ In Out 9 8100 5 4500 9000 2700
Rule: Multiply by 900 In Out 9 8100 5 4500 10 9000 3 2700
500
Write the number closest to the sum: 9,953 + 7,818 16,000 17,000 18,000 20,000 Write a number model for the estimate above
Number closest to the sum: 18,000 Number model estimate: 10,000 + 8,000 = 18,000
500
32 x 90
2880
500
45.67 - 29.84
15.83
500
Rule:______ In Out 8 640 320 9 160
In Out 8 640 4 320 9 720 2 160
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