An interesting way of dividing numbers by 2 from left to right


It is very easy and you may do it in your mind.

Divide each digit by 2, if its left digit (the previous digit) is odd then add 5 to it. And if the original number is an odd number add 0.5 to the end of your result.

Example: Take 1234 to divide it by 2

a) 1 / 2 -->> 0 (the first digit from left is 1, and it does not have any digit at its left)

b) 2 / 2 -->> 1 + 5=6 (the second digit from left is 2, and its left digit is odd)

c) 3 / 2 -->> 1 =1 (the third digit from left is 3, and its left digit is even)

d) 4 / 2 -->> 2 + 5 = 7 (the forth digit from left is 4, and its left digit is odd)

So the answer is: 617


Another example: Take 78463 to divide it by 2

a) 7÷2 --> 3 (the first digit from left is 7, and it does not have any digit at its left)

b) 8÷2 --> 4+5 (the second digit from left is 8, and its left digit is odd)

c) 4÷2 --> 2 (the third digit from left is 4, and its left digit is even)

d) 6÷2 --> 3 (the forth digit from left is 6, and its left digit is even)

e) 3÷2 --> 1 (the fifth digit from left is 3, and its left digit is even)

f) As 78463 is an odd number, we add 0.5 to the end of our result.

So the answer is: 39231.5


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Mental Math for Faster Calculation

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