A logic problem by Christopher Boo

Logic Level 1

A B C B C A + C A B 0 \begin{array} { rrrr } & & A & B & C \\ & & B & C & A \\ &+ & C & A & B \\ \hline & & &\phantom0 & \end{array}

In the cryptogram above, A , B , A,B, and C C are each single-digit integers that are not necessarily all distinct. Which of the following is a possible value of the final sum?

665 666 667 668

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22 solutions

Sunil Pradhan
Jun 4, 2017

Relevant wiki: Cryptogram

ABC + BCA+CBA = 100(A+B+C) +10(A+B+C) +1(A+B+C) = 111(A+b+C) so answer is multiple of 111 so option is 666

odd answer to an odd problem

Jarrid Fraley - 4 years ago

don't expect people to enjoy or understand that jiberish

Bob Bade - 4 years ago
Marta Reece
May 30, 2017

All three columns are effectively the same, with a sum A + B + C A+B+C .

There is no carry-over digit from the first column, since there is no column in front of it, so there cannot be any carry-over in any of the other columns either.

Therefore all the digits must be the same.

The only answer satisfying that condition is 666 \boxed{666} .

This solution can be actually realized, for example by setting A = 1 , B = 2 , C = 3 A=1, B=2, C=3 .

You can just set A=B=C=2

aaaaaaa aaaaaa - 4 years ago

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Since it says "not necessarily all distinct" you could. But the point of including the possible setting of A=1, B=2, C=3 was to show that there is a way to get the number 666, not to provide the only way of doing it.

Marta Reece - 4 years ago

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you have a point. but i said u could define a=b=c=2 because thats more quickly to think if u gave the attention to the "not necessarily all distinct" (on my conception)

aaaaaaa aaaaaa - 4 years ago
Scott Rodham
Jun 4, 2017

Since A, B and C appear in each column, then their total is 111*(A+B+C) and 111 divides 666

This makes no sense

Jake Toomer - 4 years ago

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Why do you say so?

Pi Han Goh - 4 years ago
Shady Damaty
Jun 5, 2017

Each column is the same so the sum must also be the same (assuming no sum larger than 9 as evidenced in the proposed solutions). Process of elimination reveals 666 is only possible answer.

I couldn't follow what you said. What process of elimination steps did you do? Why couldn't the answer be 665, 667 or 668?

Pi Han Goh - 4 years ago

ABC=100A+10B+1C ,BCA=100B+10C+1A ,CAB=100C+10A+1B . SO,NOW,

ABC+BCA+CAB=

100(A+B+C)+10(A+B+C)+1(A+B+C)=

(100+10+1)(A+B+C)=111(A+B+C)

So the answer must be a multiple of 111 Hence,the anwer is 666.

Right. By rewriting the cryptogram into an equation makes it so much familiar and easier to work with.

Pi Han Goh - 4 years ago
T B
Jun 8, 2017

Relevant wiki: Cryptogram

You can rearrange this cryptogram to A A A B B B + C C C 0 \begin{array} { rrrr } & & A & A & A \\ & & B & B & B \\ &+ & C & C & C \\ \hline & & &\phantom0 & \end{array} Than each column has A+B+C, so the answer is 666

Yes! The fun thing with this kind of cryptograms is that you can rearrange the column in any order.

Christopher Boo - 4 years ago
Surya Subbarao
Jun 9, 2017

If you rearrange the digits of a number, when take its remainder when it is divided by 3, the remainder stays the same. Therefore, ABC, BCA, and CAB must have the same remainder when divided by 3. No matter if this remainder is 0, 1, or 2, when we add the same remainders three times, we will get a multiple of 3, because 0+0+0=0, 1+1+1=3, and 2+2+2=6. Therefore, the answer has to be a multiple of 3, and the only answer choice which satisfies this is 666.

RIght, that's a good approach to show that the final sum is divisible by 3.

Can you also show that the final sum is divisible by 37?

Pi Han Goh - 4 years ago
Peter Macgregor
Jun 5, 2017

Relevant wiki: Divisibility Rules (2,3,5,7,11,13,17,19,...)

The digital root of each of the three numbers is, by definition, A+B+C (modulo 9)

And so the sum of the three numbers has digital root 3(A+B+C) (modulo 9).

So the digital root of the total is a multiple of 3.

This is a well known test for divisibility by 3, and the only choice satisfying this criterion is 666 \boxed{666}

In that case, is it possible that the final sum could also be 222 (since 222 is also divisible by 3)?

Pi Han Goh - 4 years ago
Daryoush Soltani
Jun 11, 2017

100A+10B+C+100B+10C+A+100C+10A+B=111A+111B+111C=111(A+B+C) 666 is the only possible answer.

In addition, associative property holds. So, no matter what the order is the answers will be same in each row vertically as A,B,C are present in each vertical row.

If it is helpful then pls upvote.

Nick Hounsome
Jun 11, 2017

Since every column sums the same 3 digits the only way that the answer is not 3 identical digits is if A+B+C > 9 but if that were true the answer would be 4 digits. The only answer with 3 digits all the same is 666.

If you separate each character with a line, you get a MS Excel table. This leads you to a different point of view: know you can see rows and columns of characters. Whatever, when you read the equations in every possible direction up down and down up, left to right and right to left, you always get some kind of palindromic equations of this shape: (A+B+C)=(B+C+A)=(C+A+B)=6 And then I'm becomes x=x=x=6 And x=6 So x=6/(3 equal valued single-digits )=6/3=2

Check, 2+2+2=6 in 3 columns of this visual palindromic equation I told before. The result is definitely 666 with this demonstration 👹

Let me know you comments! But please forgive my poor English🙏

I get what you mean, but notice that it's not necessary to make A=B=C=6/3=2. Another way is A=1, B=2 and C=3.

Christopher Boo - 4 years ago
John T Reagan
Jun 8, 2017

I found the phrase "not necessarily all distinct" confusing. What is that saying?

I like all the solutions given below, but a combination of Scott Rodham's and Marta Reece's answers come closest to the solution I found. I just looked at the possible answers and they all started with 6. So, that left 1 + 2 + 3 as the only possible combination for the columns making 666 the only possible answer.

As a side note, this kind of highlights why multiple choice questions lack when it comes to assessing student's knowledge.

Not necessarily all distinct allows another solution where A=B=C=2.

Christopher Boo - 4 years ago
Stephen Bush
Jun 7, 2017

A, B, and C are limited within digits 1 - 9. One can eliminate digits - 4, 5, 6, 7, 8, and 9 for A, B, or C; since the 1st two columns add up to 6. So the inequality: 1 < = A or B or C < = 3 holds. I have zero background in this subject - I'm just an signatures/electric engineer. Cheers!

Good reasoning, except why we can eliminate the digit 4? Isn't A=4, B=1, C=1 one of the solution?

Christopher Boo - 4 years ago
Spartan Jay
Jun 7, 2017

Since the first row has to add up to 6 and there's 3 letters 6 divided 3 is 2 So each letter is 2

Note that they do not necessarily have to be the same, ie A=1, B=2, C=3 works.

Christopher Boo - 4 years ago
Mehjabin Mahira
Jun 7, 2017

If we assume A=1 B=2 & C=3, Most probable answer is 666

You are right. Can you identify all possible sum?

Christopher Boo - 4 years ago
Glen Jackson
Jun 6, 2017

I'm not a math person, at all (lol - that is why I am here!). I got the correct answer, but my brain is . . . odd.

A/B/C are single-digit integers, and they do not have to be distinct from each other. So the negative whole numbers from -9 through to 0 up to +9 on the positive whole number side.

Seeing that the rows & columns will work out exactly the same, the 3 numbers at the bottom will have to be identical, as well as the sum of A+B+C cannot be greater than 9. The only fitting answer is 666.

So, A/B/C could be any variation of ... what? (0,0,6), (0,3,3), (0,2,4), (1,0,5), (1,1,4), (1, 2, 3), and (2,2,2).

Negatives can't be used the way it is set up (as an addition problem); otherwise, things like (-3, 0, 9) would also work.

That's the fantastic thing about math - there's usually multiple paths to the correct answer! I also used limits and boundaries so to speak- where ABC were between 1 - 9, and from there you can eliminate several integers between 1-9.

Stephen Bush - 4 years ago
Breton Tom
Jun 6, 2017

The Given Answers were an aide to solving the Cryptogram. And using the Commutative Property, Order of Addition states the #s could be added in any order. The Problem Statement said 3 INTEGERS, that eliminated ZERO. So the 3 Digits had to be 123. 1+2+3 is going to equal 6 any order. The Sum is 666.

I thought 0 is considered an integer, though?

Glen Jackson - 4 years ago

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Yes, it is. What's your point?

Pi Han Goh - 4 years ago

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Because @Breton Tom wrote '3 INTEGERS, that eliminated ZERO' which causes confusion.

Christopher Boo - 4 years ago

The 3 digits don't HAVE to be 1,2,3

(0,0,6), (0,3,3), (0,2,4), (1,0,5), (1,1,4), (1,2,3), and (2,2,2) all work, AFAIK

Glen Jackson - 3 years, 12 months ago

A + B + C =600 so to have all the digits differ, the best choice would be 1, 2, 3. Each letter is a different number (1,2,3).

No, this is incorrect. A, B and C are single digit numbers, so their sum (A+B+C) cannot be equal to 600.

Pi Han Goh - 4 years ago
John Drake
Jun 5, 2017

Because of the commutative property of addition, each column should have the same sum value so 666 (number of the beast lol) is an obvious solution. There is, of course, the possibility of a carry, but none of the solutions fit that. If A + B + C = 15 then you'd get the answer 1,665.

Yes, another way to see there's no carry in A+B+C is that the leading digit of the result must be either 1 or 2 which doesn't fit the options.

Christopher Boo - 4 years ago
Daniel Cortild
Jun 5, 2017

We know that the solution will present itself under the form of

( A + B + C ) 100 + ( B + C + A ) 10 + ( C + A + B ) = ( A + B + C ) 111 (A+B+C)\cdot 100 + (B+C+A)\cdot 10 + (C+A+B) =(A+B+C)\cdot 111

Thus the solution is a multiple of 111 111 , thus it has to be 666 666 .

Note that it could also have been 111 , 222 , 333 , 444 , 555 , 666 , 777 , 888 , 999 111,222,333,444,555,666,777,888,999

Hmmm, are you sure the final sum could also be 111, 222 or 333? If so, what are the values of A, B and C that satisfy these values, respectively?

Pi Han Goh - 4 years ago

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Normally, when we say 3 digit integer A B C ABC we don't consider A A as 0 as that would result in a 2 digit integer. So the minimum value of A, B, C should be one, so 111 and 222 is not possible.

Nonetheless, the problem didn't state that it's a 3 digit number so I think 111 and 222 is possible with A=1, B=0, C=0 and A=2, B=0, C=0 respectively. In this case, the answer could have been 0 as well.

Christopher Boo - 4 years ago
Hana Wehbi
May 30, 2017

I assigned values to A, B and C. Since I saw the sum has 6 in any of its digits so my values should add up to 6. I said let A=1, B=2 and C =3. Thus, the possible value for X Y Z = 666 XYZ=666

You have shown that 666 is a possible answer, but why couldn't the answer be 665, 667 or 668?

Pi Han Goh - 4 years ago

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I noticed A, B or C appear in each column; therefore the number 111 111 must divide the sum which the only option works here is 666 666 .

Hana Wehbi - 4 years ago

Just set A=B=C=2 as a possible solution. Then ABC+BCA+CAB=666.

Mike Evans - 4 years ago

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