To @Zed_Girl. How ADD and SUBTRACT fast

ADDITION

First, you must know what is ENDING NUMBER

7 + 6 = 13

Do you notice this addition end in 3? This is called ending number.

8 + 7 = 15

Do you notice this addition end in 5? This is called ending number.

You must know to begin with addition all the ending numbers, and it’s a very very easy task to do. Only with practice you will memorize these features.

So, if I ask you the ending number of 8 + 9, 4 + 7 or 5 + 6 you should anwering very fast respectively 17, 11 and 11.

Practice as much as you could Zahra.

Then, when you are very confident and prepared and ready, start with two digits + two digits additions.

For example, 38 + 17.

Do you see that 8 + 7 is 15? That the ending number is 5? This means that the units sum is an amount higher than 10, right?

That’s why we have carry.

STARTING with the TENS 3 + 1 + 1 from the carry, we have 5, and from the ending number of the UNITS, we have 5 too. The answer is, then, 55.

Another example: 16 + 48

Do you see that the amount of units are higher than 10? Than 6 + 8 is 14? That 4 is the ending number and that we have a carry?

Then we start from the left, from the TENS: 1 + 4 + 1 from the carry give us 6.

6 in the TENS and 4 as ending number of the UNITS. Then we have 64 as the answer.

Feel free to ask whatever question if you don’t understand @Zed_Girl

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