Is it Today? Yesterday? Tomorrow?

Logic Level 4

When the day after tomorrow becomes yesterday, it will be as far from Saturday as last Friday will be from today, if today becomes yesterday. What day of the week is it?

Friday Thursday Wednesday Monday Saturday Sunday Tuesday

A P by A P , 19, USA

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1 solution

A P
May 28, 2016

Say today is n n , where Monday = 1 =1 , Tuesday = 2 =2 ...Saturday = 6 =6 , Sunday = 7 =7 . Also, last Sunday = 0 =0 , last Saturday = − 1 =-1 and last Friday = − 2 =-2 . When the day after tomorrow is yesterday, it will be n + 3 n+3 . When the today is yesterday, it will be n − 1 n-1 . The problem claims that the difference between n − 1 n-1 and − 2 -2 (last Friday) is equal to the difference between 6 6 (Saturday) and n + 3 n+3 . Therefore we have n − 1 − ( − 2 ) = 6 − ( n + 3 ) n-1-(-2)=6-(n+3) . Solving, we have 2 n = 2 2n=2 , so n = 1 n=1 , or Monday.

4 Helpful 0 Interesting 0 Brilliant 0 Confused

Forgive me for the following questions.

1: When the day after tomorrow is yesterday. How is this possible? You answered Monday, so the day after tomorrow on a Monday would be a Wednesday. Wednesday is definitely not right before Monday.

2: How is Monday equidistant from Friday and Saturday if Monday equals Wednesday? Think of it this way: If we are looking at distance between Monday and the Friday before Monday, and the Saturday after Monday, then the distance between M and F is 3 and between M and S is 5. If we are looking at distance between Monday and the Friday after Monday, and the Saturday before Monday, then the distance between M and F is 4 and between M and S is 2. See? It doesn't make sense either way!

This is totally illegal in my view.

Also regarding your solution:

  1. If today is n, then shouldn't the day after tomorrow be n+2? If the day after tomorrow is equal to yesterday, then n+2 = n-1 which does not make sense.

  2. Your next step is based off the flawed assumption.

Maybe I'm just not understanding your solution, but I tried your solution on the calendar and it doesn't seem to work.

Hobart Pao - 5 years ago

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  1. Let's say today is Monday. When Monday becomes yesterday, it will be Tuesday. Apply that logic to the day after tomorrow in this question, Wednesday. Therefore Wednesday will become yesterday on Thursday.
  2. The question clearly states that when the day after tomorrow will be yesterday (Thursday), it will be equidistant from Saturday, which is 2 days, as Friday will be from yesterday (Sunday), which also 2 days. Which part are you confused about?

A P - 5 years ago

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Oh I see. Maybe you should rephrase and use "become" instead of "is"? I see what you mean now. When you use "is", it seems kind of paradoxical.

Hobart Pao - 5 years ago

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@Hobart Pao – Ok got it.

A P - 5 years ago

Also "if today is yesterday" could be rephrased because that also makes absolutely no sense.

Hobart Pao - 5 years ago

You could also put a clarification of the statement before entering in the calculation. Something like , in three days there will be the same number of days until Saturday as last anyway Friday until yesterday anyway. So the subject of this is between , after 3 days and yesterday which are equidistant from Saturday and last anyway Friday. So between n+3 and n-1 where n is anyway the day considered and so on to clarify the ambiguous statement better I think.

A A - 5 years ago

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