Addition becomes easy when we add any number with ten or
multiples of ten. For example 23+10=33, 23+40=63, 23+70=99.Therefore, task of
addition becomes easy when we look for numbers that add to ten and then look at
the rest of the numbers for addition to this rounded figure of ten.
For
example: 9+4+2+3+1 in this sum of series of numbers, it will make
our task easy if we perceive to add 4+2+3+1 to ten and then add this ten to
rest of the number 9 to make the answer equal to 19. Likewise if we see any
numbers which add to multiples of ten then those numbers be added first and
then the remaining numbers be added.
For
example: 13+7+ 3+5+2+29+1+8 here 13 and 7 can be added to make it
20, 3+5+2 can be added to make it 10, 29+ 1 can be added to make it 30.So
20+10+30 becomes 60. Now 60+8 addition is easy. Let us try to take few more
examples to make the point clear.
3+5+4+3= Add 1st, 3rd, and 4th number
to make it 10. Add the remaining number 5 to make sum total equal to 15.
If the numbers do not have tens or multiple of ten, they
can be made so.
For
example:
59+79 =50+70+9+9 = 120+18 = 138
48+58 = 40+50+8+8 = 90+16 = 96
Another method of treating the numbers as ten or multiples
of ten is deduction or addition method. For example 78 can be treated as 80 and
added to another number but the resultant will have to be lesser by 2 as we had
increased it fictitiously by 2.