The price of a new mobile phone model is $450. During a launch
special where it was sold at a discounted price, the number of mobile phones sold increased by 80%. The total sales from all the mobile phones sold increased by 12%. Find the percentage discount on the original price of the mobile phone, correct to 1 decimal place.
revenue = price * quantity, so at discount d,
450d*1.80q = 450q*1.12
d = 0.622
so that's a discount of 37.8%