Read the following table : What is the ratio of the most common and rarest…

In a frequency table, the ratio between two categories is formed by taking their respective values in the order the question asks for, and then reducing that ratio to its simplest form by dividing both terms by their greatest common divisor (GCD).

1. From the table, Blood Group O has 12 students, the highest count among all four groups, so O is the most common blood group.

2. Blood Group AB has 3 students, the lowest count among all four groups, so AB is the rarest blood group.

3. Form the ratio of the most common group to the rarest group, in that order: 12 : 3.

4. Divide both terms by their GCD, 3: 12 ÷ 3 : 3 ÷ 3 = 4 : 1.

As an independent check, add all four counts: 9 + 6 + 12 + 3 = 30, which matches the total given in the table, confirming the counts were read correctly; scaling 4 : 1 back up by 3 also recovers 12 : 3.

Hence, the ratio of the most common to the rarest blood group is 4 : 1.