Toyota Yaris Problems

THE law allows for an error of plus/minus 10 per cent on speedo readings and yours falls within that tolerance. While it clearly annoys you I don't think it's much of a problem and you have suggested three ways of dealing with it. If you drove at the indicated speed you wouldn't break the law, which is probably the best solution. You could guess and that would probably mean a speeding ticket or two. Or you could calculate the error and allow for it. You only have to calculate the error for three speeds, 60, 80 and 100km/h and then either remember them or tape them on your dash.