Mathematics magical tricks

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sakshi pendharkar
Mathematics magical tricks

Here are a few math tricks that you might find helpful:

  1. Multiplying by 9: To multiply a number by 9, simply multiply the number by 10 and then subtract the original number. For example, to find the product of 9 and 6, you can multiply 6 by 10 (60) and then subtract 6 from that (54).

  2. Squaring a number ending in 5: To square a number ending in 5, take the tens digit and multiply it by the next highest number, and then append 25 to the end. For example, to find the square of 35, you can take the tens digit (3) and multiply it by the next highest number (4) to get 12, and then append 25 to get 1225.

  3. Multiplying by 11: To multiply a number by 11, add the digits of the number together and put the sum in the middle, with the first and last digits remaining the same. For example, to find the product of 11 and 23, you can add 2 + 3 to get 5, and then put 5 in the middle of the original number to get 253.

  4. Divisibility by 3: A number is divisible by 3 if the sum of its digits is divisible by 3. For example, 456 is divisible by 3 because 4 + 5 + 6 = 15, which is divisible by 3.

  5. Divisibility by 9: A number is divisible by 9 if the sum of its digits is divisible by 9. For example, 729 is divisible by 9 because 7 + 2 + 9 = 18, which is divisible by 9.

  6. Finding percentages: To find a percentage of a number, you can multiply the number by the percentage as a decimal. For example, to find 20% of 150, you can multiply 150 by 0.2 to get 30.

  7. Finding square roots: To find the square root of a number, you can guess and check using perfect squares. For example, to find the square root of 61, you can guess that it is between 7 and 8, and then try 7.5. Squaring 7.5 gives you 56.25, which is too low, so you can try 7.6. Squaring 7.6 gives you 57.76, which is too high, so you can try 7.55. Squaring 7.55 gives you 57.3025, which is close to 61, so you can try 7.56. Squaring 7.56 gives you 57.7536, which is even closer to 61, so you can stop there and say that the square root of 61 is approximately 7.56.

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