Zoo Feeding — Direct Proportional Scaling

A zoo feeds 8 penguins with 24 kg and 4 sea lions with 24 kg per week. The question asks for fish needed for 4 penguins AND 8 sea lions — both quantities have changed from the given values. The key is the unitary method: find the per-animal rate first, then scale to the new count.

Unitary method / scaling ratio problems appear frequently at the easy end of OC MR. A common trap is treating the given totals as fixed and adding them (24 + 24 = 48), forgetting that the animal counts have changed. Students who convert to per-animal rates first never fall for this.

The examiner tests whether students can apply the unitary method across two different animal types simultaneously. Option C (48) traps students who only compute the sea lion fish (8 × 6 = 48) and forget the penguins. Option A (12) traps students who only compute the penguin fish.

Two groups are given with their total consumption (or cost, etc.). The question then changes the group sizes and asks for a new combined total. Students must find the per-unit rate for each group, scale to the new size, then add the two results.