$A$ and $B$ together can do a work in $12$ days; $B$ and $C$ together in $15$ days; $A$ and $C$ together in $20$ days. All three together will finish it in:

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Aicharya · Accepted Answer

Adding all three: $2(A + B + C) = \dfrac{1}{12} + \dfrac{1}{15} + \dfrac{1}{20} = \dfrac{5 + 4 + 3}{60} = \dfrac{12}{60} = \dfrac{1}{5}$. So $A + B + C = \dfrac{1}{10}$. All three take $10$ days.

$A$ and $B$ together can do a work in $12$ days; $B$ and $C$ together in $15$ days; $A$ and $C$ together in…

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