Maths can’t really reveal the secret of telepathy (reading people’s minds), but some clever maths tricks make it seem like it is possible. Some of these will need a calculator. Examples are in square brackets but try them with other numbers and read people’s minds!

#### The Answer is Three

- Think of a whole number (an integer) bigger than zero [e.g. 4]
- Square it (multiply it by itself) [16]
- Add the original number [20]
- Divide by the original number [5]
- Add 17 [22]
- Take away the original number [18]
- Divide by six [3]
- The answer is always three.

#### The Answer is Five

- Think of a whole number bigger than zero [e.g. 2]
- Multiply it by two [4]
- Add 10 [14]
- Divide by two [7]
- Take away the original number [5]
- The answer is always five.

#### Guess Two Numbers

- Pick a number from one to nine [e.g. 8]
- Double it [16]
- Add five [21]
- Multiply by five [105]
- Pick another number from one to nine and add it [e.g. 2 – 107]
- To guess the two numbers, subtract 25 from the total [82] – the first digit is the first number and the second digit is the second number.

#### The Grey Elephant From Denmark

- Pick a number from five to nine [e.g. 9]
- Take away five [4]
- Multiply by three [12]
- Square the number (multiply it by itself) [144]
- If the answer is higher than ten, add the digits together to get a single number [1+4+4=9).
- If the resulting number is less than five, add five – if it is more than five, subtract four [5]
- Multiply by two [10]
- Subtract six [4]
- Pick the letter of the alphabet that corresponds with the number (e.g. A=1, B=2)
- Pick a country beginning with the letter
- Pick a animal that begins with the second letter of the country
- What colour is the animal?

This doesn’t work every time, but most people will be thinking about a grey elephant from Denmark. Why? The answer to the numbers part is always four, so the letter chosen is always ‘D’. Most people seem to choose ‘Denmark’ and a grey elephant.

#### Guess a Three Digit Number

- Pick a three digit number [e.g. 123]
- Multiply by seven [861]
- Multiply by 11 [9471]
- Multiply by 13 [123123]
- The answer will be the original number twice.

#### Guess the Date

- Pick a date [e.g. 1 January 2009]
- Add 18 to the chosen month [19]
- Multiply by 25 [475]
- Subtract 333 [142]
- Multiply by eight [1136]
- Subtract 554 [582]
- Divide by two [291]
- Add the chosen day [292]
- Multiply by five [1460]
- Add 692 [2152]
- Multiply by 20 [43040]
- Add the last two digits of the chosen year [43049]
- Subtract 32940 [10109]
- The answer is the date in month/day/year format

#### Guess the Seven Digit Number

- Pick a seven digit number [e.g. 1234567]
- Multiply the first three digits by 80 [9840]
- Add one [9841]
- Multiply by 250 [2460250]
- Add the last four digits of the chosen number [2464817]
- Add the last four digits of the chosen number again [2469384]
- Subtract 250 [2469134]
- Divide by two [1234567]
- The answer is the original number