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12th Grade > Mathematics

BINOMIAL THEOREM MCQs

Binomial Theorem

Total Questions : 74 | Page 8 of 8 pages
Question 71. In (32+133)n if the ratio of 7th term from the beginning to the 7th term from the end is  16, then n =
  1.    7
  2.    8
  3.    9
  4.    None of these
 Discuss Question
Answer: Option C. -> 9
:
C
16=nC6(213)n6(313)6nCn6(213)6(313)n6
61=613(n12)
n12=3
n=9
Question 72. If the coefficients of pth, (p+1)th and (p+2)th terms in the expansion of (1+x)n are in A.P., then
  1.    n2−2np+4p2 = 0
  2.    n2−n(4p+1)+4p2−2 = 0
  3.    n2−n(4p+1)+4p2 = 0
  4.    None of these
 Discuss Question
Answer: Option B. -> n2−n(4p+1)+4p2−2 = 0
:
B
2ncp=ncp1+pcp+12(np)!P!=1(np+1)!(p1)!+1(np1)!(p+1)!2(np)p=1(np+1)(np)+1(p+1)ponsimplifingwegetn2n(4p+1)+4p22=0
Question 73. If coefficient of (2r+3)th and (r1)th terms in the expansion of (1+x)15 are equal, then value of r is
  1.    5
  2.    6
  3.    4
  4.    3
 Discuss Question
Answer: Option A. -> 5
:
A
15C2r+2 =15Cr2
But15C2r+2 =15C15(2r+2) =15C132r
15C132r =15Cr2 ⇒ r = 5.
Question 74. The sum of coefficients of the last six terms in the expansion of (1+x)11 is
  1.    256
  2.    512
  3.    1024
  4.    2048
 Discuss Question
Answer: Option C. -> 1024
:
C
The coefficients of the last six terms of (1+x)11 are
11C0,11C1,11C2....11C5
Sum=11C0+11C1+11C2+11C3+11C4+11C5=1+11+55+165+330+462=1024

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