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Permutations And Combinations

Question
CBSEENMA11014067

Find x, if fraction numerator 1 over denominator 6 factorial end fraction plus fraction numerator 1 over denominator 7 factorial end fraction equals fraction numerator straight x over denominator 8 factorial end fraction

Solution
fraction numerator 1 over denominator 6 factorial end fraction plus fraction numerator 1 over denominator 7 factorial end fraction space equals space fraction numerator straight x over denominator 8 factorial end fraction
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#6 {main}</pre>

rightwards double arrow      1 over 1 plus 1 over 7 space equals space straight x over 56
Multiplying throughout by 56, we get
rightwards double arrow                  56 + 8 = x
∴                             x = 64.

Some More Questions From Permutations and Combinations Chapter

Determine K, so that K + 2, 4K – 6 and 3K – 2 are three consecutive terms of an A.P.