To find out how many zookeepers are needed for 228 monkeys, we can set up a ratio based on the information given. For every 12 monkeys, the zoo hires 3 zookeepers.
First, we can find how many groups of 12 monkeys there are in 228 monkeys:
\[ \text{Number of groups} = \frac{228 \text{ monkeys}}{12 \text{ monkeys/group}} = 19 \text{ groups} \]
Next, since each group of 12 monkeys requires 3 zookeepers, we can calculate the total number of zookeepers needed:
\[ \text{Total zookeepers} = 19 \text{ groups} \times 3 \text{ zookeepers/group} = 57 \text{ zookeepers} \]
Therefore, the zoo needs 57 zookeepers.