Sunday Times Teaser 2869 – Cubic Savings
by Danny Roth
Published September 17, 2017 (link)
In 2009 George and Martha had a four-figure number of pounds in a special savings account (interest being paid into a separate current account). At the end of the year they decided to give some of it away, the gift being shared equally among their seven grandchildren, with each grandchild getting a whole number of pounds. At the end of the following year they did a similar thing with a different-sized gift, but again each grandchild received an equal whole number of pounds. They have repeated this procedure at the end of every year since.
The surprising thing is that, at all times, the number of pounds in the savings account has been a perfect cube.
What is the largest single gift received by any grandchild?
Sadly, this teaser appears to have a flaw as there are two possible solutions.
Some feel that one of the two solutions is eliminated by the phrase “… each grandchild getting a whole number of pounds”, which they interpret to imply a number of £s greater than one. But I don’t agree since, in my view, £1 is a whole number of £s.
Jim Randell has suggested that one way of rescuing it would be to require that none of the gifts to the grandchildren are themselves perfect cubes (see here).