In a seminar, the number of participants in Hindi, English and mathematics are 60, 84 and 108 respectively.

Minimum number of rooms required $=\frac{\text { Total number of participants }}{\operatorname{HCF}(60,84,108)}$

Prime factorization of 60, 84 and 108 is:

$60=2^{2} \times 3 \times 5$

$84=2^{2} \times 3 \times 7$

$108=2^{2} \times 3^{3}$

$\mathrm{HCF}=$ product of smallest power of each common prime factor in the numbers $=2^{2} \times 3=12$

Total number of paricipants = 60 + 84 + 108 = 252

Therefore, minimum number of rooms required $=\frac{252}{12}=21$

Thus, minimum number of rooms required is 21.