Sunday Times Teaser 2920 – Barcode

by Ian Gilchrist

Published September 9 2018 (link)

When Fred opened his “10 to 99 Store” (the numbers reflecting the prices of the goods in pounds) there was trouble from the start when the barcode reader scanned the prices backwards. First at the self-service checkout was Mrs Adams, who kept quiet when she was charged £59.49 for a £94.95 item. The next two customers, Mr Baker and Mr Coles, paid by card, without noticing they had in fact been overcharged. All three had bought a differently-priced item, and by coincidence, in the case of the two men, the price each had been charged was a whole multiple of the actual price.

How much had the shop lost or gained overall on the three transaction?