math
2nd Grade - Adding and subtracting

Grade 2 lesson

1 - Adding and subtracting


Addition

1 - Adding without carrying

We have already seen the simple additions, now let us see how to add large numbers easily. To calculate easily 1245+3541, first you have to place the two numbers one below the other ligning up the units numbers, you write the symbol + and you draw a line below the two numbers.
put an addition
Then you add the units numbers. 5+1=6 so you write down 6 below the line.
put an addition
You do the same with the tens numbers. 4+4=8 so you write 8 below the line.
put an addition
You do the same with the hundreds numbers. 2+5=7 so you write 7 below the line.
put an addition
Finally, you add the thousands numbers. 1+3=4 so you write 4 below the line.
put an addition
This way you can now read the result below the line : 1245+3541=4786.

Train yourself!
Use this method to answer the following question :
What is the value of 499 + 300 ?


2 - Adding and carrying

Sometimes, when adding two numbers of a same column, you find a result larger than 10. For example with the addition 2455+1927, 5+7=12
put an addition
In this case, do not write 12 below the line but only 2, and the 1 is written on the top of the column on the left. It is called carrying and you then have to add it with the tens column.
put an addition
Now you add the tens column, with the number you carried, 1+5+2=8 so you write 8 below the line.
put an addition
Then you add the hundreds numbers, since you get a number bigger than 10, you write 3 below the line and you carry the proper number :
put an addition
Finally, you add the thousands column without forgetting the number you carried. You can conclude that 2455+1927=4382.
put an addition


Go on training yourself!
Use this method to answer the following question :
What is the value of 382 + 608 ?


Now that you know how to add, let's learn how to subtract.

Subtraction

1 - Subtraction without carrying

To calculate a complicated subtraction, you start as you do with when adding : you write down the two numbers one below the other, ligning up the numbers of unities, but also writing the biggest number before. We calculate 476-145.
put a subtraction
Start with the units column. Count how many you need to get from the number below to the number on the top. Here, from 5 to 6 you need 1 so you have to write 1 below the line.
put a subtraction
Then you do the same for the tens column : from 4 to 7 you need 3 so you write a 3 below the line.
put a subtraction
Finally for the hundreds column, from 1 to 4 you need 3 so you write the number 3 below the line. You can read the final result of the subtraction: 476-145=331.
put a subtraction


To train yourself
Use this method to answer the following question :
What is the value of 498 - 036 ?


2 - Subtracting and carrying

Sometimes, in a column, the number on top is smaller than the one below. For example, for 752-318 you should start, for the units column, with calculating "from 8 to get to 2". It is not possible.
put a subtraction
When you are in this situation, you add 1 before the number on top, and 1 on the right of the number below in the column on the left.
put a subtraction
Next, you count "from 8 to get to 12". The result is 4 so you write 4 below the line.
put a subtraction
For the tens column you cannot count "from 1 to 5" as you have to add to 1 the number you have just carried over. So you count "from 2 to 5". The result is 3, so you place a 3 below the line.
put a subtraction
Finally, for the hundreds column, you count "from 3 to get to 7". The result is 4 so you place the number 4 below the line and you can read the final result of the subtraction : 752-318=434.
put a subtraction


Go on training yourself!
Use this method to answer the following question :
What is the value of 847 - 319 ?






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