Reading People’s Minds

  • By: The DIG for Kids
  • Time to read: 2 min.

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]
  • How Do Magicians Read Minds?
  • 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

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