Mathematics Made Easy: Faster Addition
H.D. Motiramani
Addition becomes always easy if any two numbers are added in such a manner that it becomes a whole number 10 or a multiple of 10. For example, if we need to add 6+4+7+3+8+3+7+5+4+1, we add in combination of numbers like 6 and 4 to make it a whole ten, we then add 7 and 3 to make it ten, then 8 and 3 do not make it a whole ten so we look ahead to number 7 and 3, thereafter 5,4 and 1 will again make it a whole. In this example of summation, it can be observed that we came across four times ten. While doing such additions the number 8 that we left is not to be forgotten. So the total of this sum becomes 48.
When we look for numbers to make it a whole, the two numbers together can be ten or twenty or thirty. More and more examples will make the point clear. If there are numbers 16+7+4 the answer becomes very easy if 16 and 4 are added first in mind to make it 20. Then the left out 7 will make a total as 27. While addition, we need not follow a set sequence of left to right or right to left. We have to look for addition by looking at whole tens or twenties or so. Let us take another example 27+43. Here we need to add 7 and 3 to make it ten. Then 20+40 make 60 and that add this 7+3= 10 will give an answer 70. In this example 7+3 made a perfect ten, however even if the number was say 27+49, we need to add 20 and 40 to make it 60 and then 7+9=16 to make it a total 76.
Practicing such a method of addition by looking at the numbers to make a whole will make the mental addition quicker. Let us make ten more examples to make the point clear.
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Look for multiples of 10 & Add |
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S.N. |
Questions |
Answers |
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1 |
1+2+9 |
Add 9&1first then add the left out 2,Ans=12 |
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2 |
6+2+4+3 |
Add 6&4first then 2&3 to make Ans= 15 |
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3 |
6+9+2+2 |
Add 6,2,2 first and then9 to get Ans=19 |
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4 |
3+4+5+5+7 |
Add 5&5, 3&7 and 4 to get the Ans=24 |
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5 |
48+22+3 |
Add 48 & 22 first to make it 70 then add 3 Ans=73 |
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6 |
49+33+1 |
Make 49+1=50, then add 33 to get the Ans=83 |
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7 |
37+55 |
In such questions, consider 37 as 40 add to 55 and then deduct 3 from 95 to get the Ans= 92 |
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8 |
92+75 |
Treat the first no. as 90, add 75 to get 165. Now add 2 because 92 was made 90, Ans = 167 |
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9 |
79+26 |
80-1+26=106-1=105 |
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10 |
57+98 |
60-3+98=158-3=155 |
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