Sunday, 23 July 2017

5 basic Maths Tricks

                   5 basic Maths Tricks

Squaring numbers with ‘5’ at one’s place

The trick is applicable if you are squaring a two digit number that has 5 at one’s place. It is certain that the last two digits of the answer will be 25 in case your two digit number ends in 5. Now the remaining digits of the answer can be calculated by multiplying the first digit of the number by its successor. For example say find the square of 85. The last two digits of the answer is 25 and the initial digits would be 8*9= 72 (9 being successor of 8). So, the final answer is 7225.

Multiplication with multiples of 5

Whenever we are multiplying a given number with 5 or multiples of 5, replace 5 with a multiple of 10 divided by an integer. In case you want to calculate 43*25, simply rewrite the sum as 43*100/4 where 25 is replaced by 100/4. Now, it is easier to calculate 4300/4, which comes out to be 1075.

Multiplication involving 9

This trick is a direct application of distributive property of multiplication, where you can directly multiply a given number with a multiple of 10 and then subtract the given number. For instance, to find 57* 999, simply calculate 57*(1000-1). Therefore the sum reduces to 57000- 57=56943.

Multiplication with powers of 2

If you are performing multiplication of a number with 2 or multiples of 2, then just double the given number for each power of 2 in the multiplier. To solve 13* 16, all you need is to first rewrite the sum as 13*2*2*2*2. Now you have to double 13 four times to get the result, the first doubling of 13 gives 26, the second gives 52, the third doubling gives 104 and the fourth doubling gives 208.

Using binary and bisect trick

If you need to find the product of two numbers one of which is even, then simply double one number and halve the even number till you reach a much simpler calculation. Instead of multiplying 63*24, you can do 126*12, again 252*6, and further 504*3 = 1512.

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