यदि \(^{n}P_r=20\times{}^{n}C_r\) हो तो (r) का संभावित मान क्या है?
If \(^{n}P_r=20\times{}^{n}C_r\), what is the possible value of (r)?
Explanation opens after your attempt
B. (4)
Concept
The relation is \(^{n}P_r=^{n}C_r r!\), and (20) is not equal to any (r!) for these options. With these options the question would be invalid.
Why this answer is correct
The correct answer is B. (4). The relation is \(^{n}P_r=^{n}C_r r!\), and (20) is not equal to any (r!) for these options. With these options the question would be invalid.
Exam Tip
संबंध \(^{n}P_r=^{n}C_r r!\) है और (4!=24) नहीं बल्कि (20) किसी (r!) के बराबर नहीं है। दिए गए विकल्पों में कोई सटीक नहीं है इसलिए यह प्रश्न अमान्य होता यदि विकल्प यही हों।
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