We can solve the problem of multiplication by simply repeated addition also, but at times when we have larger digits, this method of repeated addition does not work. Here we will discuss how to do 3 digit multiplication.
For multiplying a three digit number with another number of one digit, we will first place the digits of the multiplicand under their respective place values and in the next row we write the digit of the multiplier. Thus every digit of the multiplicand is multiplied by the multiplier and in case the number is greater than 9, i.e. in two digits, then the digit at the tens place is transferred to the next place value and added their with the product. Let us look at the following example: 125 * 5,
H t o
1 2 5
X 5
5 2 5
Now we will learn how a three digit number is multiplied by a two digit number. In this case we will first write the number in two rows at their proper place so that the product of 204 * 12 looks as follows:
H T O
2 0 4
X 1 2
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4 0 8 (Here we will multiply the multiplicand with the ones place of the multiplier i.e. 2. Now we will write 0 at the ones place in the next row).
2 0 4 x (and then multiply 204 by 1, which is at the tens place of the number 12)
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2 4 4 8 ( this is the product of 204 and 12, which we will get by adding the digits in the two rows. )
In this way we get the product of the three digit number with a two digit number, and here we observe 204 X 12 = 2448.