Estimating Sums and Differences
What is the answer when you estimate the sum of:
524 + 811
1,300
23x5
115
2.3 + 0.64
2.94
Rule = x90
Input: Output:
3
5
1,800
Input: Output:
3 270
5 45
20 1,800
0.4 + 12.6 = 1.66
Didn´t line up decimals, place value.
13
What is the answer when you estimate the sum of:
745 + 355
1,100
37*9
333
23.907
Rule: *300
Input: Output:
3
5
15,000
Rule: *300
Input: Output:
3 900
5 1,500
50 15,000
40 x 50 = 200
4x5= 20, so there is only 1 x10 added.
There should be two.
40 x 50 = 2,000
What is the answer when you estimate the sum of:
123 + 599
700
253 x 4
1012
8.045 + 8.45
Rule: ?
Input: Output:
4 240
6
Rule: x60
Input: Output:
4 240
6 360
1 - 0.32 = 1.32
added, didn´t subtract
0.68
What is the answer when you estimate the difference of:
987 - 311
835 * 6
34.1 - 0.82
33.28
Rule: ?
Input: Output:
50 2,500
30,000
Rule: x50
Input: Output:
50 2,500
600 30,000
Estimate the sum:
349 + 794 = 1,200
Didn´t round 349 down to 300.
3oo + 800 = 1,100
What is the answer when you estimate the difference of:
1099 - 99
1,000
5,796
2 - 0.11
1.89
Rule: ?
Input: Output:
7 490
56,000
Rule: 70
Input: Output:
7 490
800 56,000
55 x 78 = 845
Didn´t move the 2nd set of answers over and add a zero in the ones.
4,490