September 2nd, 2009 by Math Tricks | Filed under Addition Tricks.

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When you learned how to do math in school, you probably learned how to do it from right to left.  One of the secrets to doing fast math tricks in your head is to learn how to solve mathematical problems from left to right.

Actually, learning this math tricks method is not very difficult.  In fact, your brain is already hard-wired for solving math problems from left to right; you have spent years reading left to right, correct?  Well, then your brain is trained to think from left to right – so lets try it with some simple addition problems!

45 + 38

This is a very easy problem, and it is even easier if you solve it from left to right.  First, break down the number 38 into it’s tens and ones:

30 + 8

Now add the numbers in this fashion:

45 + 30
75 + 8 = 83

So the full breakdown of the problem looks like this:

45 + 38 =
45 + (30 + 8)

Once you have the problem in this format, it is much easier to solve.

384 + 467

Once again, to solve this problem, break it down into more manageable parts, and then solve:

384 + (400 + 60 + 7)

= 784 + (60 + 7)

= 844 + 7

= 851

### 5 Responses to “Addition Tricks – Addition from Left To Right”

1. Mahesh Dharmawardane | 23/12/10

Dr. Steven Pomeroy suggested good method to add two numbers. I have got suggestion in adding two three digits number.

Ex. Let’s consider the same problem mention above.

384+467 ?

384+ 467 = (300+400)+ (80+60)+ (4+7)
= 700+140+11
= 851

2. nancy | 12/06/12

vry much easy!

3. Leo D. | 10/07/13

@Mahesh Dharmawardane, they’re both more or less the same. The advantage of posted method is that it requires no more additions or remembering than elementary addition, three additions and one variable, whereas the response method requires five additions and two variables. It really isn’t a huge difference with small numbers though.

Method 1: 384 + 467 = 384 + 400 + 60 + 7

10 Make store.
20 Put 384 in store.
40 Put result (784) in store.
60 Put result (844) in store.
80 Put result (851) in store.
90 Return store.

Method 2: 384 + 467 = (300 + 400) + (80 + 60) + (4 + 7)

110 Make store A.
120 Put 300 in store A.
130 Add 400 to store A.
140 Put result (700) in store A.
150 Make store B.
160 Put 80 in store B.
170 Add 60 to store B.
180 Put result (140) in store B.
190 Add store B to store A.
200 Put result (840) in store A.
210 Put 4 in store B.
220 Add 7 to store B.
230 Put result (11) in store B.
240 Add store B to store A.
250 Put result (855) in store A.
260 Return store A.

4. Vi | 28/07/14

In example #1, where did the 75 come from? Is that a typo?

I am definitely old school and just added a column of seven numbers with three to five digits the old way. I getting ready to double check it out on a calculator this time. Seems complicated when you are adding longer columns.

5. Vi | 28/07/14

The numbers in my problem are 4500 plus 17200 plus 621 plus 4725 plus 2278 plus 9997 plus 14766. These are dollars and cents, I just left the decimal off.

Thank you

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