Tamil Nadu Board of Secondary EducationHSC Commerce Class 11

If nPr = 1680 and nCr = 70, find n and r. - Business Mathematics and Statistics

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Sum

If nPr = 1680 and nCr = 70, find n and r.

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Solution

Given that nPr = 1680, nCr = 70

We know that nCr = `("nP"_"r")/("r"!)`

`70 = 1680/("r!")`

r! = `1680/70` = 24

r! = 4 × 3 × 2 × 1 = 4!

∴ r = 4

Concept: Combinations
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Chapter 2: Algebra - Exercise 2.4 [Page 38]

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