Viral Singapore High School Math Problem (Spoiler)

[darklord700]

http://www.theguardian.com/science/a...hat-went-viral

Can you solve it?

[Fighting Banana Slug]

I think so. Do we need to put in a spoiler alert?

[darklord700]

I put spoiler in the title and the answer is on the net already. Apparently, there are two answers depending on the assumption you make.

[V]

I see white and gold.

[Fighting Banana Slug]

D'uh. I like these logic questions, but I apparently failed at reading comprehension.

Edit: I come up with one distinct answer. I am curious assumption I am making that leads me to it.

[polak]

Don't rush and math

[Ben_in_Canada]

They`re going to grade 10 year old on this question?

[rd_aaron]

I think I got it:

Spoiler!

Answer: July 16

It can't be May or June, because Bernard doesn't know at first, and he'd know the birthdate if it was May 19 or June 18 (only one "18" and one "19).

Bernard couldn't have been given 14 because he wouldn't know if it was July or August. He knows the birthdate because the other number (either "15", "16", or "17") was eliminated in May & June. So that gives us July 16, August 15, or August 17.

For Albert to now know the answer, it would have to be July 16 since July 14th was eliminated as per the above. It can't be August 15th or 17th because Albert wouldn't have been able to figure out which of those two it was.

[Fighting Banana Slug]

I think rd_aaron has it.

[Oling_Roachinen]

Spoiler!

Hmm, because Albert knows Bernard doesn't know, we know that the month is July or August, as May and June have unique days. Bernard uses that and is able to solve, so it can't be the 14th of either month. That leaves July 16, August 15 and August 17. Since Bernard figures it out when Albert knows it, we know it can't be August because it has 2 answers. So July 16?

Edit: Took a bit longer than rd_aaron, but I got the same :P

[polak]

Ahh I see where I screwed up now.

[darklord700]

There's a second answer which Polak got depedning on the assumption you make.

Spoiler!

Alberta heard Bernard say Bernard doesn't know, so Alberta knows it cannot be May 19 and June 18. It also cannot be June 17 otherwise Albert would have known at that stage.

Bernard at that stage knows the remaining possible dates are:

May 15, 16
July 14, 16
August, 14, 15 & 17

And since Bernard declares he knows, it is only possible if Cheryl tells Bernard the 17th date, so August 17 is also the correct answer.

[darklord700]

Originally Posted by polak

Ahh I see where I screwed up now.

You didn't. There're actually two possible answers.

[polak]

Originally Posted by darklord700

There's a second answer which Polak got depedning on the assumption you make.

Spoiler!

Alberta heard Bernard say Bernard does know, so Alberta knows it cannot be May 19 and June 18. It also cannot be June 17 otherwise Albert would have known at that stage.

Bernard at that stage knows the remaining possible dates are:

May 15, 16
July 14, 16
August, 14, 15 & 17

And since Bernard declares he know, it is only possible if Cheryl tells Bernard the 17th date, so August 17 is also the correct answer.

Haha this hurts my head. I tried to pick the "right one" many times and I confused myself with my own line of thinking multiple times and had to restart.

[darklord700]

The difference between the two answers is that in the first one you assume Albert knows without Bernard telling him that Bernard doesn't know.

And in the second one, you assume Bernard tells Albert that Bernard doesn't know.

Clear as mud?

[FlamesAddiction]

Are Albert, Cheryl and Bernard common names in Singapore?

[Wormius]

Spoiler!

I think it is May 19th, since that is the only date with a unique day (19th) of them all.

Hmm, maybe not. Looks like there is more to it than I thought.

[Locke]

There are FOUR lights!

[Galakanokis]

I think Cheryl is a bitch for playing two friends off of each other....

Spoiler!

Has to be the July 16th otherwise how do you eliminate Aug 15?


My take.

May15 May16 may19
June17 June18
July14 July16
Aug14 Aug15 Aug17

First statement eliminates May and June as they have singular dates, 18 and 19.

July14 July 16
Aug14 Aug15 Aug17

Second statement eliminates the date of the 14th as it is duplicated.

July16
Aug15 Aug16

At this point we are back to eliminating the month and since there is only one date in July it has to be July 16th. Otherwise how do we determine if it is the 15 or 17?

[TheyCallMeBruce]

Originally Posted by FlamesAddiction

Are Albert, Cheryl and Bernard common names in Singapore?

No, ching chong and ping pong are more common.