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Question: The number of odd proper divisors of 3<sup>p</sup>. 6<sup>m</sup>.21<sup>n</sup> is-...

The number of odd proper divisors of 3p. 6m.21n is-

A

(p+1) (m+1) (n+1) – 2

B

(p + m + n + 1) (n + 1) –1

C

(p + 1) (m+1) (n+1) – 1

D

None of these

Answer

(p + m + n + 1) (n + 1) –1

Explanation

Solution

3p. 6m.21n = 2m.3p+m+n.7n

\ the required number of proper divisors

= Number of selections of any number of 3’sand 7’s

[Q for odd divisors 2 must not be selected]

= (p + m + n + 1) (n + 1) –1