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The Actuary The magazine of the Institute & Faculty of Actuaries

Letters: Don Shore

Tut-tut to the originator of Puzzle 388 (March 2008, p44). It is too simplistic to say in the solution that “when the homeowner stated that her ‘oldest’ child is sleeping she was giving the census-taker the fact that there is an oldest.”

Out of any three normally born children there is always an oldest, even if two are twins or all three are triplets. The rejected solution (that where the two older children have the same age in years) only holds false if the births of the children of the same age were concurrent.

In my experience of normal births (leaving aside perhaps Siamese twins or a delivery by Caesarean operation), not only is one twin actually born before the other, the mother can remember which of them came first. It is therefore totally feasible that the discarded solution is the correct one. That it might be less probable is, of course, a different matter.

Don Shore
3 March 2008

The editorial team welcomes readers’ letters but reserves the right to edit them for publication. Please e-mail letters@the-actuary.org.uk