math
posted by TUHITUHI .
by selling 90 computer a shopkeeper gains the amount which is equal to the selling price of 10 computer find the profit percent ? had he purchased them for rupees 30000 each what would have been the selling price of a computer ??

if he purchases them for p and sells them for s,
90(sp) = 10s
90s  90p = 10s
80s = 90p
s = 9/8 p = 1.125p
so profit is 12.5%
9/8 * 30000 = 33750