Class 11 Mathematics Permutations and Combinations Derivations of formulas and their connections Expert Level 64

यदि \({}^{20}C_{3r-1}={}^{20}C_{r+5}\) और indices equal नहीं हैं, तो (r) क्या होगा?

If \({}^{20}C_{3r-1}={}^{20}C_{r+5}\) and the indices are not equal, what is (r)?

Explanation opens after your attempt
Correct Answer

B. (4)

Step 1

Concept

Unequal equal-combination indices are complementary, so (3r-1+r+5=20). In exams set the sum of lower indices equal to the upper index.

Step 2

Why this answer is correct

The correct answer is B. (4). Unequal equal-combination indices are complementary, so (3r-1+r+5=20). In exams set the sum of lower indices equal to the upper index.

Step 3

Exam Tip

Unequal equal-combination indices complementary होते हैं, इसलिए (3r-1+r+5=20)। परीक्षा में lower indices का sum upper index के बराबर करें।

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यदि \({}^{20}C_{3r-1}={}^{20}C_{r+5}\) और indices equal नहीं हैं, तो (r) क्या होगा? / If \({}^{20}C_{3r-1}={}^{20}C_{r+5}\) and the indices are not equal, what is (r)?

Correct Answer: B. (4). Explanation: Unequal equal-combination indices complementary होते हैं, इसलिए (3r-1+r+5=20)। परीक्षा में lower indices का sum upper index के बराबर करें। / Unequal equal-combination indices are complementary, so (3r-1+r+5=20). In exams set the sum of lower indices equal to the upper index.

Which concept should I revise for this Mathematics MCQ?

Unequal equal-combination indices are complementary, so (3r-1+r+5=20). In exams set the sum of lower indices equal to the upper index.

What exam hint can help solve this Mathematics question?

Unequal equal-combination indices complementary होते हैं, इसलिए (3r-1+r+5=20)। परीक्षा में lower indices का sum upper index के बराबर करें।