The cake is a liar! Part 2

Logic Level 3

Alan, Ben, Chris, Dave and Emma are eating a big cake, once again. After eating, there was one slice left, and they decided to leave it for Frank but someone ate it! Frank asks each person who ate the cake and they said:

Alan said: "It wasn't Ben. It was Chris."
Ben said: "It wasn't Alan. It was Dave."
Chris said: "It wasn't Dave. It wasn't Ben."
Dave said: It wasn't Emma. It was Alan."
Emma said: "It wasn't Chris. It was Dave."

If exactly 5 of the sentences are true, who ate the cake this time?!

Also, please check Part 1 , Part 3 and Part 4 .

Chris It was no one! David Emma Ben Alan

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

5 solutions

Chew-Seong Cheong
Jun 24, 2015

Let us assume who ate the cake one by one and check the number of statements that are true. For example, if Alan ate the cake, then the first statement of Alan was true and the second one is false; both statements of Ben were false; both the statements of Chris were true and so on. And doing the same with Ben, Chris, Dave and Emma. We assign a true statement with 1 and false one with 0, we get the following table.

From the table we see that only if Emma \boxed{\text{Emma}} ate the cake that we have exactly 5 5 true statements.

Moderator note:

Nice table to tabulate the truth of each statement. You could improve it by stating what each of the columns are, to easily see why they are true or false.

It says David BTW.

Xiaoying Qin - 5 years, 7 months ago
Dhruva Patil
Jun 24, 2015

Let us group some sentences [A-Alan, B-Ben, C-Chris, D-Dave, E-Emma]

Contradictory sentences (If one is right, the other in the pair is wrong):-

It wasn't A <=> It was A

It wasn't D<=> It was D x2 (there are 2 such sentences)

It wasn't C<=> It was C

Other sentences:-

It wasn't B x2 (there are 2 such sentences)

It wasn't E

Total=>10 sentences out of which only 5 are true.

If D was the culprit, we would have 7 true sentences.

If A or C was the culprit, we would have 6 true statements.

If B was the culprit, we would have 4 true statements.

The only assumption that'll satisfy the initial conditions is assuming E (Emma) was the culprit.

Hey nice job :D

Jack Smith - 5 years, 11 months ago

Log in to reply

Nice question!

Dhruva Patil - 5 years, 11 months ago
Saya Suka
Feb 16, 2021

Everyone was defended by another friend (by the nots in their wasn't), including Ben who was defended twice by Alan and Chris. If Ben was guilty, then only 4 of those defensive statements are right and they would need a true accusation against him to make it to the fifth truths, but nobody did accuse Ben, lucky him.

If someone other than Ben was guilty, then 5 of those defensive statements are right and they would NOT need another true accusation against the guilty party to make it to the fifth truths. Amongst the other four, nobody did accuse Emma, so she must be the cake slice thief.

Rebecca Riley
Aug 9, 2015

I'm only 13 but read that emma just said who it wasnt not who she thinks it is. I did no maths, I just had a logical guess!

Irving Ekaputra
Jul 2, 2015

There are so many "was"-es, yet only 1, or none of them, is true.

And "was" and "wasn't" statements for the same name, cannot fall under the same category. ("It wasn't Alan" and "It was Alan." cannot both be true.)

We have 4 "was" statements, and 6 "wasn't" statements. Most of the "was" statements would be false, because only 1 person ate the cake.

Let's start by assuming that all 4 "was" statements, are false. Which would mean "It wasn't Chris, Dave, nor Alan.". AND 1 of the remaining statements, is false.

We're left with Ben, Emma. If it was Ben, then, "It wasn't Ben" would be false. And here's the key, we have 2 "It wasn't Ben" statements.

But only ONE of the remaining statements, is false. Which means, Ben is not guilty.

And Emma, is the cake-eater.

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...