...is the claim made on Facebook above the following logic problem:

1 + 4 = 5

2 + 5 = 12

3 + 6 = 21

5 + 8 = ??

I get 37.

1 + 4 = 5

2 + 5 = 12

3 + 6 = 21

5 + 8 = ??

I get 37.

Pancakes are delicious.

- casinterest
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- TheFlyingDisk
**Posts:**984**Joined:**

2 + 5 = 7

3 + 6 = 9

5 + 8 = 13

Seriously, this is basic stuff.

3 + 6 = 9

5 + 8 = 13

Seriously, this is basic stuff.

Everyone on the Facebook thread seems to have gotten 34 or 45.

I'm the only one out there (I think) who got 37.

I'm the only one out there (I think) who got 37.

Pancakes are delicious.

45... When do you show our explanation?

There is something special about planes....

The correct answer is 45.

For those who get 45:

Formula is x + y = z, where the result is taken by doing x + (x * y) = z.

Therefore, 1 + 4 = 1 + (1 * 4) = 5. For the last row, 5 + 8 = 5 + (5 * 8) = 45.

This is the ONLY correct answer which works for any x and y values.

For those who get 34:

Formula is x + y = z, where the result is taken by doing x + y + ("result from previous row") = z.

Using that, 5 + 8 = 5 + 8 + 21 = 34. However,**there is a row missing for 4 + 7** so you cannot prove that this is the formula.

This DOES NOT work for all x and y values since you need information on previous instances, which negates the premise of a formula.

It's a silly problem, as it's not mathematically correct and the lack of information means it sort of has two answers, as I've shown, if you assume that only the rows presented exist in the problem.

For those who get 45:

Formula is x + y = z, where the result is taken by doing x + (x * y) = z.

Therefore, 1 + 4 = 1 + (1 * 4) = 5. For the last row, 5 + 8 = 5 + (5 * 8) = 45.

This is the ONLY correct answer which works for any x and y values.

For those who get 34:

Formula is x + y = z, where the result is taken by doing x + y + ("result from previous row") = z.

Using that, 5 + 8 = 5 + 8 + 21 = 34. However,

This DOES NOT work for all x and y values since you need information on previous instances, which negates the premise of a formula.

It's a silly problem, as it's not mathematically correct and the lack of information means it sort of has two answers, as I've shown, if you assume that only the rows presented exist in the problem.

Last edited by ANITIX87 on Mon Mar 13, 2017 2:59 pm, edited 1 time in total.

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- casinterest
**Posts:**6129**Joined:**

Airstud wrote:Everyone on the Facebook thread seems to have gotten 34 or 45.

I'm the only one out there (I think) who got 37.

I could make a strong argument for 37. but it includes making an assumption of the questioners intent on missing a line. So I stand by 45

Older than I just was ,and younger than I will soo be.

casinterest wrote:I could make a strong argument for 37. but it includes making an assumption of the questioners intent on missing a line. So I stand by 45

How can you make an argument for 37? I put in the argument for 34, but I can't get 37 no matter what assumptions I make.

If you assume the missing row using the formula for 34, you get:

3 + 6 = 21

4 + 7 = 32

5 + 8 = 45

Last edited by ANITIX87 on Mon Mar 13, 2017 3:06 pm, edited 1 time in total.

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- casinterest
**Posts:**6129**Joined:**

ANITIX87 wrote:casinterest wrote:I could make a strong argument for 37. but it includes making an assumption of the questioners intent on missing a line. So I stand by 45

How can you make an argument for 37? I put in the argument for 34, but I can't get 37 no matter what assumptions I make.

If you assume that the real equation is N=(x+(y*z)) where y is the line number. so the last line would be 5+(4*8)=37 Like I said, it works out, but it is not logical based on the fact that the missing numbers (4+7) would fall apart if reintroduced.

Older than I just was ,and younger than I will soo be.

casinterest wrote:If you assume that the real equation is N=(x+(y*z)) where y is the line number. so the last line would be 5+(4*8)=37 Like I said, it works out, but it is not logical based on the fact that the missing numbers (4+7) would fall apart if reintroduced.

Interesting, my mind never went in that direction. As the row numbers aren't shown, I didn't even entertain the idea of using them. As you say, the logic falls apart when considering the lack of 4 + 7.

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ANITIX87 wrote:casinterest wrote:I could make a strong argument for 37. but it includes making an assumption of the questioners intent on missing a line. So I stand by 45

How can you make an argument for 37? I put in the argument for 34, but I can't get 37 no matter what assumptions I make.

In each statement; the 2nd operand is multiplied by +1 to said multiplier in the previous statement. Hence 8 → 32.

Edit: casinterest & I clicked submit at the same time :-/

Pancakes are delicious.

ANITIX87 wrote:there is a row missing

[...]

It's a silly problem, as it's not mathematically correct and the lack of information means it sort of has two answers, as I've shown, if you assume that only the rows presented exist in the problem.

My issue is with the assumption it is requiring you to make. If one is required to assume that a missing row is to be included in the final answer then the answer could also be "infinity" as you could logically equally assume that every row thereafter should be included.

Tugg

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- casinterest
**Posts:**6129**Joined:**

ANITIX87 wrote:casinterest wrote:If you assume that the real equation is N=(x+(y*z)) where y is the line number. so the last line would be 5+(4*8)=37 Like I said, it works out, but it is not logical based on the fact that the missing numbers (4+7) would fall apart if reintroduced.

Interesting, my mind never went in that direction. .

If you have ever debugged enough code, you will learn your mind has to examine all the possibilities. Off by one errors are prevalent is software engineering.

Older than I just was ,and younger than I will soo be.

45. I just took that online IQ test (139), it was full of these.

- AirPacific747
**Posts:**9586**Joined:**

45 for sure. First you multiply the first digit with the second, then you add the first digit to the multiplied number. It didn't seem very difficult as it was easy to pick up the logic using the examples above.

- Dreadnought
**Posts:**10201**Joined:**

34

Democrats haven't been this angry since we took away their slaves.

- afterburner
**Posts:**1107**Joined:**

Airstud wrote:Everyone on the Facebook thread seems to have gotten 34 or 45.

I'm the only one out there (I think) who got 37.

37 for me.

Wait. I changed my mind. It's 45.

ANITIX87 wrote:It's a silly problem, as it's not mathematically correct and the lack of information means it sort of has two answers, as I've shown, if you assume that only the rows presented exist in the problem.

Yeah. I got 45, but the way it's written is just so dumb. Someone trying to be way too cute with a "logic" problem.

Restoring Penn State's transportation heritage...

- TheFlyingDisk
**Posts:**984**Joined:**

ANITIX87 wrote:The correct answer is 45.

For those who get 45:

Formula is x + y = z, where the result is taken by doing x + (x * y) = z.

Therefore, 1 + 4 = 1 + (1 * 4) = 5. For the last row, 5 + 8 = 5 + (5 * 8) = 45.

This is the ONLY correct answer which works for any x and y values.

For those who get 34:

Formula is x + y = z, where the result is taken by doing x + y + ("result from previous row") = z.

Using that, 5 + 8 = 5 + 8 + 21 = 34. However,there is a row missing for 4 + 7so you cannot prove that this is the formula.

This DOES NOT work for all x and y values since you need information on previous instances, which negates the premise of a formula.

It's a silly problem, as it's not mathematically correct and the lack of information means it sort of has two answers, as I've shown, if you assume that only the rows presented exist in the problem.

4+7? Shouldn't it be

TheFlyingDisk wrote:4+7? Shouldn't it be5+7 = 12?

No, the last two rows are:

3 + 6 = 21

5 + 8 = ??

The missing row is, therefore, 4 + 7.

- TheFlyingDisk
**Posts:**984**Joined:**

ANITIX87 wrote:TheFlyingDisk wrote:4+7? Shouldn't it be5+7 = 12?

No, the last two rows are:

3 + 6 = 21

5 + 8 = ??

The missing row is, therefore, 4 + 7.

But you're assuming that a row is missing. If you assume that there's no missing rows then the answer is correct!

- DLFREEBIRD
**Posts:**808**Joined:**

i got 45 following a pattern, but since it said 97% of you would get it wrong and almost everyone here says 45

maybe the answer is hiding in plain sight and is just 12?

.

maybe the answer is hiding in plain sight and is just 12?

.

You mean 13, if we assume the line is broken due to the missing 4+7 and starts again.

DLFREEBIRD wrote:i got 45 following a pattern, but since it said 97% of you would get it wrong and almost everyone here says 45

maybe the answer is hiding in plain sight and is just 12?

.

5 plus 8 is 13.

The interesting thing is that you can be "wrong" no matter what, since the person determining if you're wrong is the person who first presents this problem, because only that person knows whether they want to pull a fast one by saying it's just 5+8=13 or making you read a formula into the entire set that you need to figure out and apply.

Restoring Penn State's transportation heritage...

TheFlyingDisk wrote:But you're assuming that a row is missing. If you assume that there's no missing rows then the answer is correct!

5+7 doesn't appear anywhere in the problem.

- TheFlyingDisk
**Posts:**984**Joined:**

ANITIX87 wrote:TheFlyingDisk wrote:But you're assuming that a row is missing. If you assume that there's no missing rows then the answer is correct!

5+7 doesn't appear anywhere in the problem.

It's 2+5+5 on the second equation

I got 45, I did it based on finding a pattern and fitting am equating to it like one of the guys above, and the "true" equation I saw was n=x*(y+1)

TheFlyingDisk wrote:It's 2+5+5 on the second equation

What? That has nothing to do with what I was saying and with what I thought you were saying. Run through the problem row by row and tell me what you're doing.

- TheFlyingDisk
**Posts:**984**Joined:**

ANITIX87 wrote:TheFlyingDisk wrote:It's 2+5+5 on the second equation

What? That has nothing to do with what I was saying and with what I thought you were saying. Run through the problem row by row and tell me what you're doing.

It's exactly what you're saying = X + Y + (result from previous row) = Z

1) 1 + 4 + (0) = 5

2) 2 + 5 + (5) = 12

3) 3 + 6 + (12) = 21

4) 5 + 8 + (21) = 34

TheFlyingDisk wrote:It's exactly what you're saying = X + Y + (result from previous row) = Z

1) 1 + 4 + (0) = 5

2) 2 + 5 + (5) = 12

3) 3 + 6 + (12) = 21

4) 5 + 8 + (21) = 34

Right, I was saying there's a row for 4+7 missing, and you corrected me to say it should be 5+7.

34 seems correct when you go with the assumption that the values given are the only one in the series. If there is indeed a 4+7 not shown, but implied, then 45 would be the only answer. Pedantic me would say that there is no indication of a missing row, like a "..." or "[...]", so I'm saying 34 is absolutely a correct answer based on the parameters provided!

Quantos,

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Feel free to comment on the sheet with any improvement suggestions and data update requests! Thanks to Paolo92 for his advice!

Feel free to comment on the sheet with any improvement suggestions and data update requests! Thanks to Paolo92 for his advice!

It's impossible to get a correct answer with a flawed formula, so the 97 per cent are not wrong at all.

Quantos wrote:34 seems correct when you go with the assumption that the values given are the only one in the series. If there is indeed a 4+7 not shown, but implied, then 45 would be the only answer. Pedantic me would say that there is no indication of a missing row, like a "..." or "[...]", so I'm saying 34 is absolutely a correct answer based on the parameters provided!

13 would make sense, if you believe the line was broken (missing 4+7) and the formula starts new with 5+8

34 would make sense, if you believe the line continues

45 would make sense, if you believe that the missing 4+7 is implied

With this not precise starting formula it is up to the person asking the question to decidce what he thinks is correct.

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