Final answer:
The original cost of the sofa set before the sales tax was added is Rs 9000. To get this, the total inclusive cost provided (Rs 10800) was divided by 1.20 (since the rate of sales tax is 20%), which corresponds to the original cost plus the tax percentage.
Step-by-step explanation:
To find the original cost of the sofa set without the sales tax, we need to work backwards from the total cost, which includes the sales tax.If the cost of a sofa inclusive of sales tax is Rs 10800, and the rate of sales tax is 20%, this means that the original cost plus 20% of it equals Rs 10800. Let's denote the original cost as 'C'. The equation can be set up as:C + (20% of C) = Rs 10800., convert the percentage to a decimal:20% = 0.2then incorporate this into the equation:C + (0.20 × C) = Rs 10800,Combine like
terms:1.20 × C = Rs 10800,Now, solve for 'C' by dividing both sides by 1.20:C = Rs 10800 / 1.20,C = Rs 900Therefore, the original cost of the sofa set before the sales tax was added is Rs 9000, which corresponds to option b in the question.To find the original cost of the sofa set, you need to subtract the sales tax from the total cost. The sales tax is 20% of the original cost, so it can be calculated by dividing the total cost by 1.2. In this case, the total cost is Rs 10800, so the original cost would be Rs 10800 ÷ 1.2 = Rs 9000.