In this blog we shall see a simple method to mentally multiply two two digit numbers which meet the following conditions:
1. The number in the units place in the two numbers must add up to 10.
2. The number in the tens place in both the numbers must be the same.
Let us see a few examples.
Let us take two numbers 17 and 13.
Note that the numbers in the unit's place in the two numbers are 7 and 3, and they add up to 10. The number in the ten's place is 1 and 1.
Let us take two other numbers 38 and 32.
Note that the numbers in the unit's place in the two numbers are 8 and 2, and they add up to 10. The number in the ten's place is 3 and 3.
Hope you have understood how to check the numbers to see whether they meet the two conditions, stated above.
Now let us take up multiplying the numbers.
Example 1
The numbers we take up are 17 and 13.
The numbers satisfy both the conditions.
Step1. Multiply 7x3 to get 21. Write this number 21, which is part of the answer.
Step 2. Now take 1 which is in the ten's place. The next higher number to 1 is 2.. 1x2 = 2.
Write this 2 to the left of 21. The final answer is 221 !
Example 2
The numbers we take up are 38 and 32.
The numbers satisfy both the conditions.
Step1. Multiply 8x2 to get 16. Write this number 16, which is part of the answer.
Step 2. Now take 3 which is in the ten's place. The next higher number to 3 is 4. 3x4=12.
Write this 12 to the left of 16. The final answer is 1216 !
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