i am getting the answer 15000 but by taking profit at the rate of (100/3)%...
because if we have opening stock 40000 and purchases 80000... this implies that we have goods worth 1,20,000 which we can sell...
now goods worth Rs. 30,000 were destroyed by fire.. and that leaves us with goods worth Rs. 90,000 to sell...
also.. if the rate of profit on sale is taken to be (100/3)%, then the rate of profit on sales will be 25%...
thus 25% of 1,00,000 is 25000...
we know selling price - profit = cost
so 1,00,000 - 25,000 = 75000..
so closing stock is 90,000 - 75,000.. that is 15,000
you get the answer a lot quicker if you solve it by making trading account.... but just check the rate of profit...