Maths · Algebra · chapter 7 of 14

Class 11 Maths Chapter 7: Binomial Theorem Assertion-reason questions with answers

2 assertion-reason questions on Binomial Theorem, each with its answer and the reason, written from the NCERT chapter. For school exams on the CBSE pattern and JEE Main, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.

Question 1
Assertion (A): The expansion of (2x + 5)20 has 21 terms. Reason (R): The expansion of (a + b)n, n a positive integer, has (n + 1) terms.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.

R is the general fact and A is R with n = 20, so both are true and R explains A.

Question 2
Assertion (A): ⁶C₀ + ⁶C₁ + ⁶C₂ + ... + ⁶C₆ = 64. Reason (R): ⁿCr = ⁿCn−r for 0 ≤ r ≤ n.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.

A is true: x = 1 in (1 + x)6 gives 26 = 64. R is true, but the symmetry of the coefficients does not give their sum; the sum comes from putting x = 1.

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