Yes, doubling then subtracting 10% of the resultant works because that is the same as multiplying by 1.8 :) When going the other way and dividing, I similarly

Yes, doubling then subtracting 10% of the resultant works because that is the same as multiplying by 1.8 :) When going the other way and dividing, I similarly find it mentally easier to multiply by 10/18 (rather than just divide by 1.8)