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