Given in question that,we have to decrease by 72%.that means from 100% of total, 72% should be decreased. that means an overall of 28% will be left. so if you make a number into 28% of it, it implies that you have decreased that number by 72%.so from this,we can say that we have to make the number 28%.that means we have to multiply the number with 28/100 which is equal to 0.28.
