Shocking new figures reveal almost one-third of Welsh parents cannot do simple maths expected of an 11-year-old. A further 16 per cent would also be at a loss to explain simple sums to their child of primary-school age.
The Assembly government this week launched Numbers Count, a huge media campaign to raise numeracy standards among adults. Ex-Catatonia star Cerys Matthews has been signed up to sing the Len Barry track '123' on a series of TV adverts, which also star rugby legend Jonathan Davies.
Adults with a numeracy problem will be urged to phone 123 123 for a self-help pack.
The booklets, one for adults, the other for adults helping children, are designed to be user-friendly.
The first allows users to test themselves, and provides a guide on how to tackle key areas such as decimals, fractions and percentages. Toni Schiavone, executive director for the Basic Skills Agency (BSA) in Wales, which is managing the campaign, said the idea was to target young parents.
He said learning how to calculate annual percentage rates could be a real money saver for families hit by debt. Brushing up on numeracy skills could also give parents confidence to help with their children's homework.
A huge drive to raise literacy and numeracy skills in Wales started in 2001 with the launch of the basic skills strategy. Last April, an advertising campaign encouraged parents to read and talk to their children.
Speaking at the numeracy campaign launch, Mr Schiavone said: "Adults often joke when they can't add up - but it is a different story with literacy."
The bilingual adverts are to be screened on prime-time TV during the commercial break for Coronation Street. In the run-up to Numbers Count, the BSA interviewed just over 1,000 parents in Wales. A quarter reported having trouble working out sums with decimal points, 36 per cent said they struggled with fractions and 31 per cent have problems with percentages.
More women reported being stumped by simple sums and lacked more confidence overall.
Everyday maths also proves difficult for a small majority of adults, with 9 per cent reporting problems reading bus timetables, 8 per cent not able to work out how good a special offer is, and 6 per cent not knowing how to split a restaurant bill. Twice as many in the lower social classes thought they were poor at maths.
Jane Davidson, education and lifelong learning minister, said 53 per cent of adults in Wales did not reach level 1 in numeracy, a benchmark for average literacy and numeracy standards. The Welsh Assembly hopes to raise the level 1 standard to 80 per cent in literacy and 55 per cent in numeracy by 2010.
Mr Schiavone said higher standards would help to end the cycle of low attainment, low-paid jobs and low aspirations in the more deprived regions of Wales.