A shopkeeper marks the price of a book $120\%$ above its cost price. If he gives a discount of $10\%$ on the marked price, then find his profit $\%$.

Let the Cost Price ($\text{CP}$) of the book be $\text{₹}100$.
The shopkeeper marks the book $120\%$ above $\text{CP}$.

$$\text{Marked Price (MP)}=100+120=\text{₹}220$$

He gives a discount of $10\%$ on the marked price:

$$\text{Discount}=10\%\text{ of }220=\frac{10}{100}\times 220=\text{₹}22$$

Therefore, the Selling Price ($\text{SP}$) is:

$$\text{SP}=\text{MP}-\text{Discount}=220-22=\text{₹}198$$

Now, calculate the profit percentage:

$$\text{Profit}=\text{SP}-\text{CP}=198-100=98$$

$$\text{Profit }\%=\frac{98}{100}\times 100=98\%$$