Percetage formulas

Can anyone help, what I have is a column with my buying costs in, next I have a column for GP% to put whatever is needed in, with the result next. IE £100 buying costs 20% GP result £125.00, what would a formula be please.

Perhaps something like:

=A2*(1+B2)

where A2 has buying cost and B2 has GP%.

Thanks for that, but I'd already got that far, that's a mark-up %, the result should be say for £1000 + 20%GP £1250. For a mark up of 20% it would be £1200.
Any ideas?