a) A mark dwon greater than 99% and less than 100%
Mark down 99.1% of x
Original price: x
Final price: original price - mark down = x - 0.991 x = 0.009x
=> If orginal price is 1000 and mark down is 99.1% , final price = 0.009*1000 = 9
You can check that the mark down is 99.1% of 1000 = 991.
b) A mark down that is less than 1%
Mark down: 0.1%
Original price: 10,000
Mark down: 10,000 * 0.1% = 10
Final price: 10,000 - 10 = 9,990
c) A mark up that is more than 200%
Mark up: 300%
Original price: 100
=> final price = 100 + 100*300% = 100 + 300 = 400