You'd be suprised how many people took their GCSE maths 10 or so years ago who stuggled back then but who now can't even remember to do simple subtraction and division.
Sorry, but if you can't manage to add/subtract/multiply/divide simple numbers you shouldn't be offered a job with anyone...you should be going straight back to school.
I recruit for a major UK airline and I'm sorry, this level of ignorance is totally unacceptable...the level of maths required in the job is BASIC (addition of meals, the odd manual currency conversion when no bar computer or calculator is available, calculating arrival times etc.) If people can't even manage this BASIC level of maths then I'm afraid they should consider getting some tuition asap.
Sounds harsh, but the truth often is.