The number of ways in which an examiner can assign 20 marks to 4 questions giving not less than 2 marks to any question is

x1+x2+x3+x4=20,xi≥2 By assigning 2 marks to each question ,we have to distribute the remaining 12 marks to 4 questionsx1+x2+x3+x4=12  Answer=12+4−1c4−1=15c3=455