I'm just back from a bit of a road trip in the US (absolutely brilliant by the way - what an amazing country! ) but the one thing I had a problem with was converting US Dollars into Pounds Sterling.
My other half, who's just so patient with my maths floopiness, tried to teach me how to work it out, and eventually saved the formula into my mobile for me to use whenever I had to.
Needless to say, I completely forgot that we'd had the conversation and of course, had no recollection of what the formula was - never mind that it was all in my phone.
Result? End of the holiday and I'm bemoaning the fact that I must have spent so much, but can't work it out, and there's stuff in the duty-free I wouldn't mind but I have no idea how to work out what it costs in Sterling. Other Half good humouredly goes through the process of working it out and, knowing I'll forget what he's told me, I get out my mobile to type it in. Which is where I discover the same formula that I typed in at the start of the holiday...