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Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationnPr & nCrHard2 minQB

MathematicsHardsingle choice

If $n$ balls of identical weight are divided into all possible groups of three, the sum of the weights of all groups is 480 g. For all possible groups of four, the corresponding sum is 640 g. Find $n$ .

Options:

Answer:

Solution:

Let each ball weigh $w$ . Then $(3 n) 3 w = 480$ and $(4 n) 4 w = 640$ . Dividing gives $\frac{n - 3}{4} \cdot \frac{4}{3} = \frac{4}{3}$ , hence $n = 7$ .

Stream:JEESubject:MathematicsTopic:Permutation & CombinationSubtopic:nPr & nCr

⏱ 2mℹ️ Source: QB

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