Class 11 Mathematics · Chapter 7 · Test 3
Combinations
50 MCQs Covers nCr, complementary combinations, the nPr and nCr relation, and permutation versus combination.
50 questions · 45 min · 50 marks
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Sample questions
The first 5 of 50. Try each one, then tap to see the answer.
Question 1
The number of combinations of n different objects taken r at a time nCr is:
- An!/r!
- Bn!/(n-r)!
- Cr!/(n-r)!
- Dn!/[r!(n-r)!]
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Answer: D
nCr = n!/[r!(n-r)!].
Question 2
The value of nCn is:
- A1
- Bn
- Cn!
- D0
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Answer: A
nCn = n!/(n! 0!) = 1.
Question 3
The value of nC0 is:
- A0
- Bn
- C1
- Dn!
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Answer: C
nC0 = n!/(0! n!) = 1.
Question 4
The complementary combination result states that nCr is equal to:
- AnC(r-1)
- BnC(n-r)
- CnP(n-r)
- D(n-r)Cn
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Answer: B
nC(n-r) = n!/[(n-r)! r!] = nCr.
Question 5
The relation between permutations and combinations is:
- AnPr = nCr/r!
- BnPr = nC(n-r)
- CnPr = n! x nCr
- Dr! x nCr = nPr
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Answer: D
nPr = n!/(n-r)! = r! x n!/[r!(n-r)!] = r! x nCr.
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