What day is it?

Logic Level 2

Yesterday, I didn't know what day it was. I asked my two brothers.
'Friday,' said Adam.
'Saturday,' said Ben.

'What is it tomorrow, then?' I asked, trying to sort it out.
'Monday,' said Ben.
'Tuesday,' said Adam.

'Oh, for heaven's sake! What day was it yesterday,' I asked.
'Wednesday,' said Adam.
'Thursday," said Ben.

If Adam and Ben each have given one correct answer and two incorrect answers, what day is it today?

From Professor Ian Stuart.

Sunday Thursday Monday Saturday

6 solutions

Nguyen Thien Vy
Jul 19, 2014

Suppose that Adam's right in YD => Ben will be right in TD or TM Similar in the other supposition. It's not hard to find that Ben said YD was Thursday and Adam said TD was Friday. This is reasonable. Therefore => Today was Friday (in the conversation). But the question was Today (not in the conversation) => It is Saturday

I couldn't quite understand the explanation.

José Manuel Júnior - 6 years, 10 months ago

"Adam's right" = the day Adam got correctly "YD" = Yesterday, "TM" = Tomorrow, and "TD" = Today.

Remember they where talking "Yesterday" (First word in the problem) but they wanted to know the day "Today" (Bottom of the problem). Therefore whatever the correct answer for Tomorrow in the conversation (neither boy said it, but we can follow Thurs-Fri-Sat and come up with the answer) is essentially "Today" and therefore the correct answer to the problem.

Harrison Bolin - 6 years, 10 months ago

Barjuan Davis
Jul 25, 2014

Let's make a simple timeline.

              -2 days ago-  |   -YESTERDAY-       |    -Now-

             Wednesday      |        Friday       |   Tuesday    

              Thursday      |        Saturday     |   Monday

Note : The first line is for Adam, while the second is for Ben. Keep it in mind.

First, let's inspect the -2 days ago- time mark. Then, check the -YESTERDAY- mark. If it is sound illogical, you can omit the answer, because it is wrong. Remember : Each of them only have ONE correct answer.

Okay, check the Adam's answer on -2 days ago- mark. It's Wednesday. In the -YESTERDAY- mark there have to be a Thursday, right? so, Wednesday is an incorrect answer from Adam; one down, three to go.

Check Ben's answer in the same mark; it's Thursday. So now we need a Friday in the -YESTERDAY- mark, and yes! We have it on Adam's answer.

Adam and Ben has got each of them the right answer, so the rest is WRONG.

so now we have this ..

              -2 days ago-  |   -YESTERDAY-       |    -Now-

                            |        Friday       |     

              Thursday      |                     |

The answer is in the -Now- time mark. You can decide based on this what the answer is.

Don't get it? I'll help. It's SATURDAY. Thursday > Friday > Saturday.

Easiest way: The intersection between the days given in conversation for TODAY and the 4 given answers for TODAY...if think logically

Axzel Tan - 6 years, 10 months ago

Skylar Saveland
Jul 18, 2014

The only answers that work together are: A says it's Friday and B says yesterday was Thursday. Since the questions were asked YESTERDAY, we know that yesterday was Friday and TODAY is Saturday.

If Today is Saturday,

Benn's case: 1. Benn answered Yesterday as Saturday and Thursday. Both are Incorrect. 2. Benn answered tomorrow as Monday. That to incorrect.. So, all three answers of Benn seems like incorrect.

Is any thing wrong in your question? If my understanding is wrong, pls correct me.

Srinivasan Govindarajan - 6 years, 10 months ago

Saturday was Ben's answer for yesterday. Thursday was Ben's answer for two days ago.

Felicia Sutandijo - 6 years, 10 months ago

Saya Suka
Feb 28, 2021

It's not difficult at all, but presenting it in an orderly way helps a lot.

Answers	Yesterday	Today	Tomorrow	True day
Adam	Wednesday	Friday	Tuesday	Friday
Ben	Thursday	Saturday	Monday	Thursday

One thing to remember is that this conversation happened yesterday, so the "today" asked for in the problem is the tomorrow from that trilogues. Answer is Saturday.

Answers	Yesterday	Today	Tomorrow	Notes
Adam 1		Friday
Ben 1		Saturday
Adam 2			Tuesday
Ben 2			Monday
Adam 3	Wednesday
Ben 3	Thursday

You can always build a table like the above and fill in the blanks to get the correct answer.

Answers	Yesterday	Today	Tomorrow	Notes
Adam 1	Thursday	Friday	Saturday	= B3
Ben 1	Friday	Saturday	Sunday
Adam 2	Sunday	Monday	Tuesday
Ben 2	Saturday	Sunday	Monday
Adam 3	Wednesday	Thursday	Friday
Ben 3	Thursday	Friday	Saturday	= A1

Annie W.
Feb 22, 2015

Note: "today" in this explanation is yesterday in the problem (for example, if I say that "today" is Friday, then the solution to the problem would be Saturday).

Situation A: Adam is right in saying that today is Friday.

Therefore, Adam is wrong in saying tomorrow is Tuesday and wrong in saying that yesterday was Wednesday. Furthermore, Ben is wrong in saying that today is Saturday, wrong in saying tomorrow is Monday, and right in saying yesterday was Thursday. These answers fit the requirements (one correct answer and two incorrect answers each), so we can suppose that today is Friday.

However, we're not done yet-the problem says that the narrator asked what day it was YESTERDAY. Therefore, today's date would be one day after the "today" in situation A. So, the correct answer would be one day after Friday, or Saturday.

Carlo Dalino
Aug 4, 2014

There is no friday in the choices which only leaves saturday as the answer.

Explain your reasoning, please?

Maddie Anderson - 6 years, 1 month ago

What day is it?

From Professor Ian Stuart.

6 solutions

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