Explain how to solve ":' Share with your friends Share 0 Abhishek Kumar answered this Dear Student, Total number of ways to draw 7 tickets in 4 drawings=74=2401Fvaourable number of ways such that in 4 drawings the sum of numbers is 8=coefficient of x8 in 1+x+x2+x3+x4+x5+x641+x+x2+x3+x4+x5+x6 is a GP with common ratio x and first term 1sum of GP 1+x+x2+x3+x4+x5+x6=1×1-x71-xHence we need to find coefficient of x8 in 1-x71-x4⇒1-x74×1-x-4⇒1-4x7+x28-4x21+6x14×1-x-4⇒1-4x7+.. as higher powers than 8×1-x-4now binomial expansion of 1-x-n using taylor series =1+nx+n×n+12!x2+n×n+1n+33!x....∞⇒1-x-n=∑k=0∞C3k+3×xkhence 1-x-4 we get =C38+3×x8+C31+3×x1+ and other powers which are not required⇒1-4x7+.. as higher powers than 8×C38+3×x8+C31+3×x1+ other powerscoefficient of 8=C38+3×x8-4×C31+3=C311-4×C34=165-16=149Hence probability=1492401 Regards, 0 View Full Answer