Parents everywhere will know the sinking feeling that comes with the question: “Can you help me with my homework?”

The heart is willing, but the mind is blank. Just what was Pythagoras’s theorem? How do you work out the area of a circle? When did the Hundred Years’ War start or finish?

Now a French publisher is inviting mothers and fathers to use their holidays to brush up on everything they were supposed to have learnt at school and have probably forgotten.

Le Cahier de Vacances Pour Adultes (Holiday Revision Guide for Adults) is designed to ensure that when lessons resume in September, parents are one step ahead of their offspring – or at least not too far behind.

The guide has become the most unexpected literary hit of the summer. Published a month ago, it has sold 90,000 copies, taking it to the top of the nonfiction bestseller chart.

Le Figaro said that France was displaying a “mad enthusiasm” for the guide. “The success is phenomenal,” Jean-Loup Chifflet, the publisher, said. “It’s replacing Su Doku and has become a gift that people give instead of flowers when they are invited to dinner.” Mr Chifflet said that the book was intended as beach-reading, but it contains heavyweight material on grammar, maths, history, geography, English and general culture.

Readers are expected to be familiar – or reacquaint themselves – with fractions, geometry and prime numbers.

They are questioned about Gallic and world history – the name of the King guillotined in 1793, the year of publication of Mein Kampf or Neil Armstrong’s arrival on the Moon, for instance.

Then they are asked about the finer points of the French language – accents, punctuation or whether to put an “s” on adjectives when the noun is plural.

In the sections on English, they are questioned about the translation of such phrases as “to get cold feet”, “to have egg on your face” and “to make no bones about it”.

Mr Chifflet said that parents were snapping up the guide because they were “keen not to be overtaken by their children”, especially in the field of mathematics.

“We tend to forget a lot of these things and you have to work at them to bring them back. People aged between 30 and 60 want to know whether they’re still at the same level as they were when they were at school. But a lot of adolescents and young adults buy it for their parents as a form of revenge for having been made to do holiday homework themselves.”

France has a long tradition of producing holiday revision guides for children, with about 3.5 million sold every year.

In a country that has a two-month summer break, most parents are concerned that their children will lose track without homework.

Isabelle Antoni, a mother of three, said: “I bought the book and we did it together as a family. It was funny and interesting and there was a little bit of competition between me and my children over this. I found out that my son is not too bad at history after all, which was nice.”

She added: “Sometimes, it’s terrible for parents having to help the children with homework. When we did the revision together, my youngest child said, ‘You see, Mum, it’s not that easy’.”

Some parents bought the book as a form of blackmail, Mr Chifflet said. “They say to their children, ‘If you do your homework, I’ll do mine. We’ll do it together’.

“When I was at primary school, the teacher used to make us do homework during the holidays. I can remember being told, ‘You can’t go to the beach until you’ve done your devoirs’.

“But holiday homework is no longer obligatory and that is why the revision guides have become so popular, I suppose.” He added: “The book is meant to be enjoyable but the French, unlike the English, don’t read just for fun. They need a cultural alibi to reassure them.

“One reason the book has been successful is that the answers are serious and provide that alibi.”

Test yourself

Questions to go with adult revision guide:

— 1 Maths Marie Claudette has a 16:9 widescreen television set. If its height is 62.2cm what is its width? What is the diagonal?

— 2 English Find the right translation for “He’s a queer fish”. a) C’est bien fait pour lui. b) Ce poisson n’est pas frais. c) C’est un drôle de type.

— 3 History In what century did the Hundred Years’ War end?

— 4 Geography What proportion of global military expenditure does the US account for? a) 10 per cent. b) 20 per cent. c) 50 per cent

— 5 Grammar Punctuate the following sentence: La nourriture anglaise C’est bien simple quand c’est chaud c’est de la bière quand c’est froid c’est de la soupe (English food it’s simple when it’s hot it’s beer when it’s cold it’s soup).

Answers 1) width: 110.6cm, diagonal: 126.9. 2) c. 3) 15th century. 4) c. 5) La nourriture anglaise? C’est bien simple: quand c’est chaud, c’est de la bière; quand c’est froid, c’est de la soupe. (English food? It’s simple: when it’s hot, it’s beer; when it’s cold, it’s soup.)

Possible questions for English parents:

—1 Maths John Smith owns a circular cricket pitch, 242 yards in diameter. What is its area in acres?

— 2 French Find the right translation for “Une capote Anglaise”. a) The bonnet of an English car. b) Raincoat. c) Condom.

— 3 History On what date was Napoleon defeated at Waterloo?

— 4 Geography What proportion of the EU agricultural budget goes on subsidising French farming? a) 5 per cent. b) 11 per cent. c) 21 per cent.

— 5 Grammar Punctuate the following sentence: We always have been we are and I hope that we always shall be detested in France (Duke of Wellington)

Answers 1) 9.5 acres. 2) c. 3) 1815. 4) c. 5) We always have been, we are, and I hope that we always shall be, detested in France.

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