There are 15 children. Each of them has a different number of chocolates from 1 to 15. If all the children having odd number of chocolates eat 1 chocolate, then what is the percentage decrease in the average number of the chocolates?

Original average = (1+15)/2 = 8. Odd numbers are 1, 3, 5, 7, 9, 11, 13, 15 (8 numbers). New values: 0, 3, 4, 7, 8, 11, 12, 15 (for odds, subtract 1). Sum = 0+2+3+5+6+9+10+13+2+4+6+8+10+12+14 = 104. New average = 104/15 = 6.933. Decrease = 8 - 6.933 = 1.066. Percentage decrease = (1.066/8) * 100 = 13.33%. Re-checking calculation: The average of 1 to 15 is 8. Sum of odd numbers is 64. If each odd number decreases by 1, the sum decreases by 8. New sum = 120 - 8 = 112. New average = 112/15 = 7.466. Decrease = 8 - 7.466 = 0.533. Percentage = 0.533/8 = 6.66%.