यदि \(^{n}C_{r-1}:{}^{n}C_r=3:5\), तो ratio derivation में कौन-सा expression उपयोगी है?
If \(^{n}C_{r-1}:{}^{n}C_r=3:5\), which expression is useful in the ratio derivation?
Explanation opens after your attempt
Correct Answer
B. \(\frac{{}^{n}C_{r-1}}{{}^{n}C_r}=\frac{r}{n-r+1}\)
Concept
Canceling factorials in consecutive combinations gives \(\frac{r}{n-r+1}\). In exams do not calculate full values in ratio questions.
Why this answer is correct
The correct answer is B. \(\frac{{}^{n}C_{r-1}}{{}^{n}C_r}=\frac{r}{n-r+1}\). Canceling factorials in consecutive combinations gives \(\frac{r}{n-r+1}\). In exams do not calculate full values in ratio questions.
Exam Tip
Consecutive combinations में factorial cancel करने पर \(\frac{r}{n-r+1}\) मिलता है। परीक्षा में ratio questions में full values न निकालें।
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