Ramesh purchased a memory card at a price of Rs. 625 including the sales tax. The rate of sales tax is 25%. If the seller has made a gain of 50%, then the cost price of the memory card is :

given, 

selling price with tax = 625

Let the cost price of memory card be $$x$$

Profit = 50%

50% of $$x$$ = $$\frac{x}{2}$$

Sales tax = 25% of selling price = $$\frac{1}{4} of (x + \frac{x}{2})$$ = $$\frac{3x}{8}$$

we know,

selling price = profit + cost price + sales tax 

625 = $$\frac{x}{2} + x + \frac{3x}{8}$$, solving this we get, 

therefore $$x$$ = 333.33

so the cost price of the memory card is Rs 333 approx 

hence option A is correct