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As we know that multiplication is the repetitive process of addition, when we add the same number again and again, the number of times a number is added in itself, is the multiplication of that number. Suppose we add 15 in 15 two times, so it becomes 15+15, we can write it as 15×2. So, basically the value will be the same in both the cases, whether you add a number in itself or multiply it with the number to show how many times you wanted to add it, both are the same cases. If we keenly observe the table of 15, we see that the digits in ‘unit digit’s place’ is always 0 or 5, and this order gets repeated respectively in the same manner.
Let’s write the table of 15 –
15×1 = 15
15×2 = 30
15×3 = 45
15×4 = 60
15×5 = 75
15×6 = 90
15×7 = 105
15×8 = 120
15×9 = 135
15×10 = 150
You can extend this table to 20 times or 30 times as per your requirement but at learning it up to 10 times is quite essential. You can also learn it up to 20 times for the safe side.
Trick to avoid error in the table of 15 –
As you know that table of higher digits can cause confusion at times. Students often get confused by higher multiplications. To avoid this mistake, you can apply some simple techniques to avoid mistakes in the table of 15.
If we keenly observe the table of 15, we see that the digits in ‘unit digit’s place’ is always 0 or 5, and this order gets repeated respectively in the same manner. So, if you suddenly start scratching your head to remember if 15×8 is 120 or 121, you can remember that the unit digit in table of 15 cannot be 1, so you can eradicate your confusions easily in this way.
Examples for practice –
Example – How to calculate 15×12 + 20×15?
Answer- We know that in the process of evaluation, we can always take the common terms outside to make the calculation easier. Here we can take 15 as common, so we get,
=15 (12+20)
= 15 × 32
= 480 is our answer.
Example – What will be 15 times of 15 and 23 subtracted from it?
Answer- From the table, we can see that 15×15 will be 225. And if we subtract 23 from it, we get 225-23 = 202 is our answer.
