By selling 30 articles, a shopkeeper gains the selling price of 9 articles. His gain percent is:

30 39 $42\frac{6}{7}$ $40\frac{3}{7}$

$42\frac{6}{7}$

Let CP of the each article be Rs. x and SP of each article be Rs. y, then 30y – 30x = 9y 30y – 9y = 30x 21y = 30x y : x = 30 : 21 CP = 21 and SP = 30 Profit = 30 – 21 = 9 Profit percentage = \(\frac{9}{21}\) × 100 = $42\frac{6}{7}$