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

\(^{20}C_3\) को \(\frac{20\cdot19\cdot18}{3!}\) लिखना किस cancellation से आता है?

Writing \(^{20}C_3\) as \(\frac{20\cdot19\cdot18}{3!}\) comes from which cancellation?

Explanation opens after your attempt
Correct Answer

A. \(\frac{20!}{3!17!}\) में (17!) cancel होता है(17!) cancels in \(\frac{20!}{3!17!}\)

Step 1

Concept

Write (20!) as \(20\cdot19\cdot18\cdot17!\) and cancel (17!). In exams do not expand large factorials fully.

Step 2

Why this answer is correct

The correct answer is A. \(\frac{20!}{3!17!}\) में (17!) cancel होता है / (17!) cancels in \(\frac{20!}{3!17!}\). Write (20!) as \(20\cdot19\cdot18\cdot17!\) and cancel (17!). In exams do not expand large factorials fully.

Step 3

Exam Tip

(20!) को \(20\cdot19\cdot18\cdot17!\) लिखकर (17!) cancel करें। परीक्षा में large factorials expand पूरा न करें।

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\(^{20}C_3\) को \(\frac{20\cdot19\cdot18}{3!}\) लिखना किस cancellation से आता है? / Writing \(^{20}C_3\) as \(\frac{20\cdot19\cdot18}{3!}\) comes from which cancellation?

Correct Answer: A. \(\frac{20!}{3!17!}\) में (17!) cancel होता है / (17!) cancels in \(\frac{20!}{3!17!}\). Explanation: (20!) को \(20\cdot19\cdot18\cdot17!\) लिखकर (17!) cancel करें। परीक्षा में large factorials expand पूरा न करें। / Write (20!) as \(20\cdot19\cdot18\cdot17!\) and cancel (17!). In exams do not expand large factorials fully.

Which concept should I revise for this Mathematics MCQ?

Write (20!) as \(20\cdot19\cdot18\cdot17!\) and cancel (17!). In exams do not expand large factorials fully.

What exam hint can help solve this Mathematics question?

(20!) को \(20\cdot19\cdot18\cdot17!\) लिखकर (17!) cancel करें। परीक्षा में large factorials expand पूरा न करें।