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How Long is a Piece of String? by Rob Eastaway and Jeremy Wyndham, Robson Books, £12.95, ISBN 1861055056 Reviewed by Roy Herbert

THAT popular saying about pessimists, optimists and partly filled glasses of water could soon disappear down the plughole. The highly diverting How Long is a Piece of String? shows that such perceptions are irrelevant – because there’s a calculation proving that full equals empty.

Rob Eastaway and Jeremy Wyndham’s book on the underlying mathematics in everyday situations and actions is more fun than a ride in a one-horse open sleigh. Or a taxi, for that matter. Anyone mystified by the way a taximeter clicks up your fare can now read about the formula that the meter uses. Others might go straight for the advice on how to make the most prize money in shows such as The Weakest Link.

It’s rare for a book about mathematics to be as engaging as this. Each section is headed by a question – Is it quicker to take the stairs? Will I catch flu next week? – the answers are a feast. And the string? Oh – that’s twice the distance from the middle to the end.