Inventory turn over ratio = (Cost of revenue form operations)/(Average inventory)
Cost of revenue form operations = Opening stock + purchase - closing inventory
= 30,000 + 1,20,000 - 50,000
= Rs. 1,00,000
Average inventory = (Opening inventory + Closing inventory)/2
= (30,000 + 50,000)/2
= 80,000/2
Rs. = 40,000
Inventory turn over ratio = 1,00,000/40,000
= 2.5 times