Three rods of the same dimension have thermal conductivities $3K$ , $2K$ and $K$ . They are arranged as shown in fig. Given below, with their ends at $100^oC, 50^oC $and $20^oC$. The temperature of their junction is ......... $^oC$

86-12

  • A

    $60$

  • B

    $70$

  • C

    $50$

  • D

    $35$

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