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Are you afraid of maths? Do you have a phobia for numbers? Would you love to learn some cool math tricks? Well, here are some cool math tricks to help you build your confidence with large numbers.
· Multiplying by 9, or 99, or 999
Multiplying by 9 is really multiplying by 10-1.
So, 9×9 is just 9x(10-1) which is 9×10-9 which is 90-9 or 81.
Let's try a harder example: 48×9 = 48×10-48 = 480-48 = 432.
To multiply by 99, you need to multiply by 100-1.
So, 48×99 = 48x(100-1) = 4800-48 = 4752.
Multiplying by 999 is similar to multiplying by 9 and by 99.
48×999 = 48x(1000-1) = 48000-48 = 47952.
· Squaring 2-digit numbers that end in 5
If a number ends in 5 then its square always ends in 25. To get the rest of the product take the left digit and multiply it by one more than itself.
45×45 ends in 25. We get the rest of the product by multiplying 45 by one more than 4. So, 4×5 = 20 and that's the rest of the product. Thus, 45×45 = 2025, which is the answer.
Similarly, to find the square of 85, simply calculate 8×9 = 72 and write down 7225 as the answer.
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| Author: sri phani kumari 21 May 2008 | Member Level: Gold Points : 2 |
good game you designed.
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| Author: Krishnan C 21 May 2008 | Member Level: Silver Points : 2 |
Good one.
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| Author: Shanthi M 29 May 2008 | Member Level: Diamond Points : 2 |
very good logic.
Your logical thinking is appreciable.
Thank you
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