Or just go straight to 30%? (Take 10% & multiply by 3) Seems easier to remember the one number than 'divide by 3 for yards then subtract 10% for meters', assum

Or just go straight to 30%? (Take 10% & multiply by 3) Seems easier to remember the one number than 'divide by 3 for yards then subtract 10% for meters', assuming you have no use for yards. (I use yards colloquially, but never as a measurement.)