Only two sums of money have digits that add up the same as their value in pence
£66, 6 shillings, 6 pence equals exactly 15,918 pence. Add up the repeated digit in '£66 6s 6d' four times over (6+6+6+6) and you get 24; add up the digits of 15,918 and you also get 24. There is exactly one other sum of money, written as repetitions of a single digit in pounds, shillings and pence, with this same property. What is it?
Reveal the answer
£44,444, 4 shillings, 4 pence. That's seven 4's, which sum to 28. Converted to pence it comes to 10,666,612, and 1+0+6+6+6+6+1+2 also sums to 28. Dudeney noted an extra coincidence: the middle four digits of 10,666,612 are '6666' — a direct echo of the other answer, £66, 6s, 6d.
— Henry Dudeney, Amusements in Mathematics — Thomas Nelson & Sons, 1917, Puzzle No. 12
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