Here’s a puzzle to test your ability to find a pattern and test it against more data.

In this table, each row across follows the same pattern of numbers. See if you can discern the pattern and fill in the missing number in the bottom row. For added challenge (or competition), time how long it takes you to complete the puzzle. Then, pass it along to someone else and see if they can solve it faster. The slower one has to cook dinner!

7 | 4 | 8 |
---|---|---|

3 | 9 | 7 |

6 | 5 | 10 |

? | 8 | 4 |

Executive functions, like planning, and spatial processing are handled by your frontal lobes.

Have you solved it yet? If not, here’s a **hint**:

If you read your figures like words in the West,

then multiply your efforts and subtract the rest.

Keep reading for the **answer and solution**.

(7x4)-8 = 20

(3x9)-7 = 20

(**3**x8)-4 = 20

The answer is **3**.

More brain teaser games:

Michelle B says

Sigh! Could not get this teaser either. However, I did get the clue (somewhat). But what I found interesting is when I did repeat mentally the explanation, my brain felt, how can I say, a sense of wellbeing, like it was being nourished. Are all brain teasers not created equal in this regard? I remember mental distress after doing other ‘brain teasers’ years back.

Alvaro says

Hi Michelle, you are probably experiencing the release of dopamine and other neurotransmitters that create that sense of wellbeing as you identified a pattern. Which is why learning, brain teasers, trading successfully, and other “brain exercise” activities can be quite addictive!

A different application, but illuminating

https://sharpbrains.com/blog/2006/10/13/the-joy-of-giving-and-the-cognitive-and-emotional-health-project-the-healthy-brain/

Maryanne Silber says

Looked at the problem differently. I didn’t get your solution…but I had fun. I said 7+4+8=19

3+9+7+19

6+5+10=21

9+4+8=21

In trying to make a second “pair” that were equal I put 9 in your empty spot.

Well…I’v always been bad at math and any form of logic. But I had fun!

Maryanne Silber says

OOOPS…I can’t type either.

3+9+7=19 also “I’ve”

Caroline says

Maryanne,

While the dopamine rush that Alvaro mentions above happens when you solve the puzzle or understand the answer (the “aha!” moment), working through the puzzle is good brain exercise in and of itself (you’re getting challenging and novel mental stimulation). And you did your math correctly with a logical pattern, so you’re not that bad at either task! The typos … well those may be more due to a lapse in attention and hand-eye coordination. Keep working and having fun with it!

shreyas says

came up with something different, in terms of a relationship. subtract each number from 9, take the absolute value of this difference, and sum them, the total is always 8 ie. 7–9=-2=2 (absolute), 4–9=-5=5, 8–9=-1=1 so 2+5+1=8

similarly in the second and third rows, sum is 8. therefore the number in the fourth row can be either 7 or 11.

convoluted solution and non-unique.

wonder what that says abt my brain!

Caroline says

You’re right, that does follow a pattern! Both you and Maryanne are finding creative solutions, which is good exercise for your brain! I think it says that your frontal lobes are in good shape — good work!

Randy says

This clue confused me:

If you do your figures from east to west,

wouldn’t that mean from right to left?

Caroline says

Goodness Randy — you’re right! I’ll change it now!

joseph knecht says

An alternate solution, since the problem doesn’t state that the numbers must be integers:

If the first number is greater than the second number, add them and then subtract the difference of the first and second number. This covers row 1 and row 3.

If the first number is less than the second number, then add them and then subtract one less than the difference. This covers row 2, and indicates 2.5 as a solution to row 4.

Caroline says

Joseph,

Interesting solution, but if you don’t know what the first number in line 4 is, how do you know which rule to follow (the rule for lines 1 & 3 or the rule for line 2)?

joseph knecht says

Caroline,

Luckily for me, there was no solution where the first number is greater than the second number.

Caroline says

Joseph,

You’re right. The solution for the first number being larger doesn’t make sense (I end up with 16=4). If the first number is smaller, it does work out, but I get 1.5 as an answer.

x+8-(8‑x-1)=4

x+8–8+x+1=4

2x+1=4

2x=3

x=1.5

Nice solution! Complicated, but it works!

joseph knecht says

Caroline,

Right you are! Thanks for the correction.

john says

1

11

21

1211

111221

312211

? whats next

Alvaro says

perhaps

13112221?

good one!

Michael says

i found a different solution

7*4=2 8

3*9=2 7

6*5=3 0, the important digit is only the last digit therefore

3*8=2 4, now 6 may have worked but each pair has an odd and an even number plus no pair is double digit.

Caroline says

Creative Michael! Following your rules, I get 3 and 8 as possible answers, without a way to choose one answer. In line 2, both 3 and 9 are odd, so keeping it even and odd in each line doesn’t work. If you can come up with another rule to make only one answer, it’ll work!

Kelly Stewart says

I didn’t get the correct answer. I got five. the way I came to this was by adding the first and third number in each row. then you take that answer and subtract 1 from the number in the “one’s” spot. excuse my lack of knowledge. the number 123 1 is the hundreds, 2 is the tens, and 3 is the ones. so subtract 1 from the ones place and I came to the answer 5.

icanrule says

I came up with 3 but I got it in a different manner. Here is the way I figured it out.

1. 7 x 4 = 28 and Subtract first number = 8

2. 3 x 9 = 27 and subtract the first number = 7.

3. 6 x 5 = 30 and subtract first number but since number can’t be zero make it 10.

4. 3 x 8 = 24 and subtract the first number = 4.

Although the 3rd rule doesn’t jive all that well it still works.

MomV says

Pattern Recognition …C is the answer I picked.

dunc says

i came up with

(7Ãƒâ€”4)-20 = 8

(3Ãƒâ€”9)-20 = 7

(5x6)-20 = 10

(3x8)-20 = 4

go figure..

Erin says

dorks.

Alvaro says

Hello Erin, I wish you the best in 2008, perhaps including a more willing attitude to take on challenges and, if you decide not to give it a try, not to insult other people in that defensive, unhelpful way. No one is perfect 🙂

Have a great holiday and we hope to see you around again.

Ines says

I thought the exact same way as Michael, and icansure:

1. 7 x 4 = 28 and Subtract first number = 8

2. 3 x 9 = 27 and subtract the first number = 7.

3. 6 x 5 = 30 and subtract first number but since number can’t be zero make it 10.

4. 3 x 8 = 24 and subtract the first number = 4.