The thread on percentages had me musing back to my first job. One of the purchasing assistants there just didn't understand reverse percentages either. With her desk top calculator, she simply deducted 12.5% to find the pre-VAT (which was 12.5% at the time) price of items. But thinking about it, she almost certainly didn't have an O level in maths. These days, she'd have that GCSE A*-C, but she still wouldn't be able to do reverse percentages.