A question paper has 2 parts A & B .Each part containing 10 question.A students has to answer 8 question from?

optional parts are the relevant here part A: 5q's from 7 part B: 4q's from 8 # of ways = 7 choose 5 * 8 choose 4 = 1470 <--------

For question paper A,out of the remaining non compulsory questions(i.e.=7),5 can be selected in 7C5 ways=21 ways.For paper B,out of remaining 8 questions,6 can be selected in 8C4=8!/4!x4!=70 ways....Therefore total number of ways=21x70=1470....

For question paper A,out of the remaining non compulsory questions(i.e.=7),5 can be selected in 7C5 ways=21 ways.For paper B,out of remaining 8 questions,6 can be selected in 8C4=8!/4!x4!=70 ways....Therefore total number of ways=21x70=1470....