Discussion

Explanation:

For a number n = a^x × b^y × c^z

Number of ways of writing n as a product of two co-prime factors = 2^m-1, where m is the number of discting prime factor of n.

1925 = 5² × 7 × 11

∴ The number of ways in which 1925 can be expressed as a product of two co-primes is 2^{3 – 1} = 4 (∵ there are 3 distinct prime factors i.e., 5, 7 and 11).

Note: The four ways in which 91091 can be expressed as a product of two co-primes is

25 × 77
11 × 175
7 × 275
1925 × 1

Hence, 4.

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