Math revision guides written to help GCSE students were found to be littered with errors
The newspaper said errors included incorrect answers to multiplication questions, a plus instead of a minus symbol in an algebra equation and a missing bracket that made a calculation incorrect.
Mastering Mathematics from Hodder Education, aimed at teenagers studying the maths GCSE of Welsh exam board WJEC, contained the worst errors, The Times reported.
An investigation by BBC One programme The One Show asked maths lecturers and PhD students at Cardiff University to check it, and they found 90 errors in 1,496 maths problems in the book and their answers, which are published separately online.
WJEC said it had not endorsed the book.
We immediately commissioned one of our expert maths editors to make correction
Lis Tribe – Hodder Education
In a statement, Lis Tribe of Hodder Education told the Press Association that errors in the book and issues with the quality of answers to questions were discovered shortly before Christmas.
"We immediately commissioned one of our expert maths editors to make corrections, so that we had them ready for the first day back in January," she said.
"The book was withdrawn from sale and a corrected edition reprinted; that version is now available again for sale. We corrected the answers, double-checked them again, and uploaded a new file to our website in the second week of January."
90 errors in 1,496 maths problems were found
Customers were told about the problem and replacement copies are being set out, Miss Tribe said.
She added: "We take the quality of our publications very seriously indeed; we work with teachers and subject experts to write and review our books; moreover, for maths we use specialist maths typesetters, proof stages are reviewed by specialist editors, and answers are checked separately.
"Or at least, they should be; clearly, something went wrong with this particular title, and we have reviewed and changed a couple of our processes to make sure this never happens again."
Miss Tribe said she was sorry that "the quality we pride ourselves in was not maintained in this case".
Customers were told about the problem and replacement copies are being set out, Miss Tribe said
Matthew Lettington, the academic who led the research, said: "That level of mistakes is unacceptable. Some of the errors we found very confusing ourselves and most students would find these particular errors highly confusing whatever their ability."
Among other errors were eight errors in 563 questions in the Revise Edexcel GCSE (9-1) maths revision workbook, published by Pearson.
Pearson said that the first printing of the book contained a small number of errors, which have been corrected. The original containing the mistakes has been recalled and destroyed.
" Errors are not acceptable in our books and we work hard and have procedures in place to produce books that are as error-free as possible, and we act quickly to correct them," a spokesman said.