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Sunday Times Teaser 3015 – Quid Quo Pro

by Victor Bryant

Published Sunday July 05 2020 (link)

In Readiland the unit of currency is the quid. Notes are available in two denominations and with these notes it is possible to make any three-figure number of quid. However, you need a mixture of the denominations to make exactly 100 quid. Furthermore, there is only one combination of denominations that will give a total of 230 quid.

What are the two denominations?

3 Comments Leave one →
  1. Brian Gladman permalink

    Here is a longer but faster solution:

  2. Tony Smith permalink

    You have not explicitly shown that there is no solution with F(a,b)>999 (however obvious that may be).

  3. Brian Gladman permalink

    Hi Tony, I don’t see the relevance of any F(a, b) value above 99. Since all values above F(a, b) can be made by summing multiples of a and/or b, I have ensured all values with three or more digits can be made.

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