Permutation and CombinationEasy
Question
If nCr denotes the number of combinations of n things taken r at a time, then the expression nCr + 1 + nCr-1 + 2 × nCr equals
Options
A.n+2Cr
B.n+2Cr+1
C.n+1Cr
D.n+1Cr+1
Solution
nCr+1 + nCr-1 + nCr + nCr
= n+1Cr+1 + n+1Cr
= n+2Cr+1.
Hence, (B) is the correct answer
= n+1Cr+1 + n+1Cr
= n+2Cr+1.
Hence, (B) is the correct answer
Create a free account to view solution
View Solution FreeMore Permutation and Combination Questions
Six identical coins are arranged in a row. The number of ways in which the number of tails is equal to the number of hea...The number of ways to put five letters in five envelopes when any one letter is kept in right envelope and four letters ...Consider a photo session of 3 teachers, 6 boys and 5 girls in a line such that no two teachers are together, boys stand ...There are 20 persons among whom two are brothers. The number of ways in which we can arrange them round a circle so that...The number of ways of arranging the letters AAAAA, BBB, CCC, D, EE & F in a row if the letter C are separated from one a...