The member of committee can be grouped exactly into 12 or 16 or 20, then the minimum of the members in the committee must be
The minimum members in the committee will be least common multiple of 12, 16 and 20
LCM of 12, 16 and 20 = 240
So, minimum members in the committee should be 240 to divide them into the exact groups of 12, 16 and 20.