How to represent a recurring decimal as a fraction.

Let’s take 0,513265132651326

This repeats 51326, which has 5 digits

So, it is 51326/99999 (5 nines)

Try it on your calculator

Multiply an even number by 6

Let’s take 6 x 8

The answer will end with 8 (the second of the numbers) and the number in front of the 8 will be a half of 8, or 4

So 6 x 8 = 48

Similarly 6 x 6 = 36

Remembering the value of Pi to 6 decimal places

Simply remember the expression “How I wish I could calculate Pi”

Write down the number of letters in each word

3 1 4 1 5 9 2 and the answer is 3,141592

Multiply any number by 11

Let’s take 423 x 11

Answer 4 (4+2) (2+3) 3 = 4653

Another one 517623 x 11

5 (5+1) (1+7) (7+6) (6+2) (2+3) 3

5 6 8 13 8 6 3

The (7+6) = 13, so the 10 is carried as a 1 to the left and added to the 8, leaving 3

5 6 9 3 8 6 3 = 5693853

Another one 6485 x 11

Answer 6 (6+4) (4+8) (8+5) 5 = 6 10 12 13 5. All you have to do now is carry the tens to the left

7 0 12 13 5 = 7 1 2 13 5 = 7 1 3 3 5 = 71335