The task is to generate the correct answer for a given math problem.

Problem: by selling an article for $ 195 , a person gains $ 45 . what is the gain % ?
30 %

Problem: a can do a piece of work in 22 days and b alone can do it in 10 days . b works at it for 5 days and then leaves . a alone can finish the remaining work in
11 days

Problem: employees of a certain company are each to receive a unique 10 - digit identification code consisting of the digits 0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , and 9 such that no digit is used more than once in any given code . in valid codes , the second digit in the code is exactly twice the first digit . how many valid codes are there ?

161,280