MENTAL ARITHMETIC: ADDITION

PROBLEMS

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1.  Add each column mentally.   Regroup to compose a multiple of 10.
1. But get to know the endings.

19 + 4 =  20 + 3 = 23   25 + 8  =  30 + 3 = 33
 
18 + 3 =  20 + 1 = 21   36 + 5  =  40 + 1 = 41
 
27 + 6 =  30 + 3 = 33   49 + 8  =  50 + 7 = 57
 
47 + 5 =  50 + 2 = 52   69 + 3  =  70 + 2 = 72
 
59 + 2 =  60 + 1 = 61   78 + 5  =  80 + 3 = 83
 
67 + 4 =  70 + 1 = 71   88 + 7  =  90 + 5 = 95
 
75 + 7 =  80 + 2 = 82   89 + 5  =  90 + 4 = 94
 
78 + 4 =  80 + 2 = 82   96 + 8  =  100 + 4 = 104
 
85 + 6 =  90 + 1 = 91   99 + 7  =  100 + 6 = 106
 
99 + 9 =  100 + 8 = 108   109 + 6  =  110 + 5 = 115

2.  Adding by endings.  Add the following from left to right.  Then
2.  check your answer by adding from right to left.

2.  a)  9 + 3 + 5 + 6 + 8 + 7 + 9 = 47

2.  b)  8 + 8 + 7 + 4 + 5 + 9 + 6 + 7 = 54

2.  c)  9 + 4 + 8 + 2 + 6 + 8 + 3 + 7 + 7 + 9 = 63

2.  d)   3 + 8 + 7 + 5 + 5 + 6 + 8 + 2 + 9 + 6 = 59

3.  Complements.  Add these as skillfully as you can.

3.  a)   7 + 3 + 2 + 8 + 5 + 1 + 9  = 35

3.  b)   6 + 3 + 7 + 4 + 2 + 1 + 10 + 8  = 41

3.  c)   9 + 21 + 24 + 7 + 6 + 3 + 8  = 78

4.  Add each column mentally.  Add the tens, then add the ones.

3.  10 + 35 = 45       50 + 34 = 84       30 + 75 = 105       64 + 70 = 134

3.  20 + 41 = 61       30 + 45 = 75       90 + 58 = 148       85 + 40 = 125

3.  30 + 27 = 57       70 + 16 = 86       80 + 64 = 144       92 + 20 = 112

3.  40 + 18 = 58       50 + 28 = 78       70 + 88 = 158       78 + 50 = 128

3.  30 + 67 = 97       40 + 57 = 97       60 + 92 = 152       31 + 80 = 111

5.  Add each column mentally.  

150 + 30 = 180       160 + 61 = 221

240 + 50 = 290       240 + 72 = 312

310 + 43 = 353       380 + 84 = 464

420 + 55 = 475       460 + 91 = 551

530 + 45 = 575       550 + 79 = 629

660 + 39 = 699       690 + 45 = 735

780 + 42 = 822       870 + 86  = 956


Add each column mentally.  Add the tens, then add the ones.

6.   7.   8.
34 + 23 = 57   65 + 72 = 137   34 + 28 = 62
57 + 32 = 89   34 + 95 = 129   57 + 36 = 93
25 + 43 = 68   85 + 71 = 156   25 + 46 = 71
41 + 55 = 96   64 + 73 = 137   18 + 55 = 73
34 + 45 = 79   96 + 83 = 179   36 + 59 = 95
66 + 42 = 108   77 + 42 = 119   44 + 57 = 101
9.   10.
85 + 56 = 141   23 + 34 + 21 = 78
78 + 55 = 133   31 + 46 + 22 = 99
36 + 89 = 125   65 + 71 + 44 = 180
94 + 57 = 151   47 + 83 + 25 = 155
78 + 84 = 162   55 + 83 + 69 = 207
67 + 88 = 155   86 + 88 + 69  = 243

Add the hundreds, then the tens, then the ones.

11.
213 + 556 = 769
524 + 354 = 878
245 + 327 = 572
837 + 526 = 1363
956 + 772 = 1728
749 + 868 = 1617

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