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← Kitchen Clock · Lesson 1 of 3

Work backward from the meal

About it

A dinner is a schedule with a fixed end. Start from the time you want to sit down and count each dish backward: the roast needs 90 minutes and 20 minutes resting, so it goes in 110 minutes before. With one oven the oven dishes cannot overlap, so they line up back to back, and the first of them sets the moment you must start.

Project planners call that chain the critical path. Everything else has slack: the salad can be made any time in the last hour. Children on LogicQuest order four dishes around one oven and find the single step that cannot wait.

The figure

Count back from the meal

an hour beforetwo hours beforesit downroast in the oven, 90 minrestsalad: any time in herein it goes: 110 minutes before
A timeline running to the moment you sit down. The roast rests for the last 20 minutes and is in the oven for the 90 before that, so it goes in 110 minutes before the meal. The salad has slack: it can be made any time in the last hour.
One question

Dinner is at 6:00. The roast needs 90 minutes in the oven and 20 minutes resting after it comes out. When does it go in?

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