A lunch promise
Your restaurant accepts prepaid lunch orders. Customers expect meals ready for collection, so adding a cook seems sensible when delays mount. Yet faster cooking can simply move the queue to the packing bench.
Consider a hypothetical service with assumed timings: 40 lunches must be ready within 60 minutes. Cooking takes one minute per meal; checking and packing take two minutes per meal. Every order is confirmed, but no meals are ready. The restaurant can pay one extra trained worker for the hour, with space for either role.
Where the extra worker helps
Option A adds a cook. Two cooks finish cooking in 40 ÷ 2 = 20 minutes. One packer still needs 40 × 2 = 80 minutes, starting when the first meal arrives after one minute. The last order is ready at minute 81, missing the promise.
Option B adds a packer. One cook finishes the last meal at minute 40. Two packers alternate arrivals, keeping pace with cooking; the final meal takes two more minutes. The predicted finish is 40 + 2 = 42 minutes. Choose the extra packer under these assumptions.
Check the handoff
Inspect the current order log’s “cooking finished” and “packed” timestamps. Gaps above two minutes, with the packer continuously busy, indicate a packing queue. Packers waiting for food contradict this explanation. Trial the extra packer and compare the last “packed” timestamp with the deadline. If completion exceeds 60 minutes, investigate interruptions or missing steps before offering that promise.
When cooking sets the pace
Now change this hypothetical service: packing takes 30 seconds and customers require readiness within 30 minutes. Two cooks finish at minute 20; packing the final pair adds one minute: 21 minutes. One cook with two packers takes 40 + 0.5 = 40.5 minutes. Choose the extra cook. Assign help to the stage that limits completion against the actual promise.