The list price of a watch is 160. A retailer bought the same watch 122.40. He got two successive discounts one at 10% and the other at a rate which was not legible. What is the second discount rate?  Choose one:
A) 12%  B) 14%  C) 15%  D) 18%  E) None of these
Retailer price = list price (1−d1/100)(1−d2/100)   ⇒ 122.40 = 160(1−10/100)(1−d2/100)   ⇒ 1−d2/100=122.40×100/160×90=0.85   ⇒ d2 = (1 - 0.85) × 100 = 15%   Answer 15%
<result>C</result>
The list price of a watch is 160. A retailer bought the same watch 122.40. He got two successive discounts one at 10% and the other at a rate which was not legible. What is the second discount rate?