A book vendor sold a book at loss of 10% . Had he sold it for Rs. 108 more, he would have earned a profit of 10% . Find the cost of the book = ?

Answer: Option B

Given loss = 10% profit = 10%
Difference of overall profit and loss = 10 - (-10) = 20%
20% of cp = sp
$$\frac{20}{100}\times \text{cp = 108}$$
20 × cp = 108 × 100
cp = $$\frac{10800}{20}$$
∴ cp = 540