Psychologists observing a shopping mall parking lot found that, on average, drivers spent 39 seconds leaving a parkin...

Halle-Diaz on July 2, 2018

Video - #14-18

Hello, When it comes to determining where certain variables cannot go, I do not understand why the instructor did not cross out Ivan as being able to join in '62. Gregg joined before Ivan, but Gregg did not join in '61 or '62. The earliest Ivan could have joined was '63. However, Ivan was crossed at only '61. Thanks!

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Mehran on July 3, 2018

Hi @Halle-Diaz, thanks for your post. Your deductions & observations are 100% correct. Notice that our instructor does not fill out every "not" rule in her master diagram. Why? For two reasons: first of all, doing so is usually too time consuming. Second, putting in every "not" rule can lead to confusion / obfuscate key deductions.

In the video, the instructor's focus is filling out known limits on the most restricted spaces at play: the first (1961) and last (1968) years. This is because there are so many limits on these two spaces that you can actually narrow down the possibilities to two or three variables, tops. This is efficient and important to understand before you dive into the questions. Many additional deductions are possible, but you don't need to mark them all down at the outset in a game like this. Figure out a good "master" set up with key deductions, then let the questions guide you.

Hope this helps! Please let us know if you have any additional questions.