The marked price of the a watch is Rs. 1600. The shopkeeper gives successive discount of 10% and x% to the customer. It the customer pays Rs. 1224 for the watch, the value of x is = ?

Answer: Option C

Marked price of watch = Rs. 1600
After 1st discount of 10%
$$\begin{array}{rl}& \text{ = 1600}\times \frac{90}{100}\\ & \text{ = Rs}\text{. 1440}\end{array}$$
Customer pays (final selling price) = Rs. 1224
$$\begin{array}{rl}& \frac{x}{100}\times 1440=\left(1440-1224\right)\\ & \frac{x}{100}\times 1440=216\\ & x=\frac{216\times 100}{1440}\\ & x=15\%\end{array}$$