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Combinations — MATHS STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 ScienceMATHSCombinations3 Marks
Question
If ${^\text{n}}\text{C}_{12}={^\text{n}}\text{C}_{5},$ Find the value of n.
✓

Answer

We have,
${^\text{n}}\text{C}_{\text{r}}=\frac{\text{n!}}{\text{r!}(\text{n}-\text{r})!}$
Hence, n = m
r = 12 and 5
Applying formula
nCp = nCq = n
Then p + q = n
⇒ nC12 = nC5
12 + 5 = n
⇒ n = 17

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