The total cost price of a certain number of identical articles is Rs 4800. By selling the articles at Rs 100 each, a profit equal to the cost price of 15 articles is made. Find the number of articles bought.
Let the number of articles bought be x.
Total cost price of x articles = Rs 4800
Cost price of one article = Rs `4800/x`
The selling price of each article = Rs 100
Selling price of x articles = Rs 100x
Given, Profit = C.P. of 15 articles
∴ 100x - 4800 = `15 xx 4800/x`
`100x^2 - 4800 = 15 xx 4800`
`x^2 - 48x - 720 = 0`
`x^2 - 60x + 12x - 720 = 0`
x(x - 60) + 12(x - 60) = 0
(x - 60)(x + 12) = 0
x = 60, -12
Since number of article cannot be negative So x = 60.
Thus the number of articles bought is 60.