Bài 9: Addition of two digit number

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Starry, this is a nice board, we can write or draw on this board with a marker.

Another interesting feature of this board is that it is mathematic.

Come on, let us learn addition of two digit number using this board.

See I have already draw square of 100 on this board.

Let us now see how to add 25 and 6. Yes yes Starry, the method is the same. As using the square of 20.
 First we put this magnetic coin on the number 25.

Now, move the coin ahead six squares in the same and next column. 1 2 3 4 5 6.

Which is square do we read Starry? Yes, 31. So 25 plus 6 equal 31.

Do you understand Starry? Ok, then let’s solve the next example, 57 plus 9.

Here, let’s put the coin on the number 57. How many square do we have to move ahead?

Yes, 9 squares.
Here we have read the number 66.

So, we can say that 57 plus 9 is equal to 66.

Isn't this  a lot of fun!!! 

Ok, now let’s look at another example.

It is 5 adding to 81. On which square should we put the coin Starry?

Yes, we start from the square 81, now let’s move the coin ahead. 1 2 3 4 5. That’s 81 plus 5 equal to 86. 

I know what you are thinking, Starry.

You are wondering. This square can be use for adding two digit number.

This will take along time.
 For example if we have to add 82 to 16.

Then you know what we have to do Starry?

Yes, we have to move the coin 82 square ahead of 16.

This will take along time.
So let’s use another method to do the addition.

16 plus 82.

First we will arrange the numbers in vertical and solve.

Write 1 in the tens place and 6 in the units place.

Next, let’s place 8 below 1 in the tens place and 2 below 6 in the units place.

First we shall add the digit in the units column 6 plus 2 is equal to 8.

Next, we have to add the digit in the tens place, we get 1 plus 8 equals 9.

So Starry, 16 plus 82 is equal to 98.
isn't it  the smart faster method Starry!

Ok, now let’s solve a few example. 
Add 23 and 61. What should we do first Starry?

We shall first arrange the numbers in proper column.

In the number 23 write 2 in the tens column and 3 in the units column. What about 61 Starry?

Yes, we write 6 below 2 in the tens place and 1 below 3 in the units place.

Now let do addition! 3 unit plus 1 unit is equal to 4 unit.

2 tens plus 6 tens is equal to 8 tens. So, 23 plus 61 is equal to 84.

Let’s solve the next example.
it is 40 plus 12.

We shall first arrange the numbers vertically and solve.

Now Starry, carry out the addition.

Yes, on adding digit in the units place, we get 0 plus 2 equal 2 unit.

Next 4 tens plus 1 tens is equal to 5 tens.
So what answer do we get Starry?

Yes, 40 plus 12 is equal to 52.

Remember Starry, it is not necessary to make columns for the tens and the units place to do addition each time.

But, it is necessary to write the digit in the correct places.

Let’s solve one example. Add 35 plus 52.

First we shall write the number 35, next write  52 below 35 exact a way that 5 is written below 3 and 2 below 5.

Let’s add the digit in the unit place first. So 5 plus 2 equals 7 units.

Next we be add the digit in the tens place. So what is the answer, Starry?

Yes 3 tens plus 5 tens is equal to 8 tens. So 35 plus 52 equals 87.

In the next example add 7 and 31. Arrange numbers vertically and solve.

Starry, do you know what be the answer it? 7 units plus 1 unit is equal to 8 units.

3 tens is written in the tens place. So 7 plus 31 equals 38.

Here is the last example. The numbers here have been a ranked vertically.

How much is 22 plus 55 equals to?

Yes Starry, 2 units plus 5 units equals 7 units, 2 tens plus 5 tens is equal to to 7 tens.

So 22 plus 55 is equal to 77.

So Starry, remember when using the vertical arrangement to add , Placing a digit is very important

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