If the three broken coins when perfect were worth 253 pence, and are now in their broken condition worth 240 pence, it should be obvious that 13/253 of the original value has been lost. And as the same fraction of each coin has been broken away, each coin has lost 13/253 of its original bulk.
29.--THE BROKEN COINS.
From Amusements in Mathematics by Henry Ernest Dudeney.