For those who don't understand Ex... Friend writes the first number: 58,412 You secretly calculate: 58,412 + 199,998 = 258,410 Write this prediction on a paper and keep it hidden. Now your friend writes a second number: 23,615 You immediately write: 76,384 Why? Because each digit adds to 9: 2 + 7 = 9 3 + 6 = 9 6 + 3 = 9 1 + 8 = 9 5 + 4 = 9 Then your friend writes another number: 40,127 You write: 59,872 Again, every digit adds to 9. Now add all five numbers: 58,412 23,615 76,384 40,127 59,872 ------ 258,410