Can You Solve This Easy Math Problem in Your Mind?
video description
21 is only divisible by 2 prime factors, meaning the 3 numbers present must be 3, 7, and 1. I then moved onto 54, which had to have a 9 in it. 54/9=6, so the other numbers are either 6 and 1 or 2 and 3. Due to the current ambiguity of the 21 column, we need more information. From here, I also noticed that the 5 had to be in the row and column involving numbers with the number 0 in the ones column. 180/5=36, and that means that the 180 column needed the 9. That means 180 column is 9, 5, 4.
120/5=24, so let's see if 1, 3, or 7 fits there. 24 is not divisible by 7, and 1 would be invalid because 120/5/1 does not equal a 1-digit number. That means it has to be 3, meaning that the other number is 8. The 120 row is 8, 5, 3.
54 is not divisible by 7, meaning that 1 has to go in the 54 row. 54/9=6, meaning that the 54 row is 6, 9, 1, and the 21 column is 1, 3, and 7. By process of elimination, the missing digit on the bottom left is 2. This means that the numbers are, left-to-right, top-to-bottom, is: 6, 9, 1, 8, 5, 3, 2, 4, 7.
Date: 2023-11-15
Related videos
• TED-Ed
Comments and reviews: 20
Saurabh
Solved in 2 mins. I first placed 9. Since 180 and 54 are multiples of 9, no other no is multiple of 9. Then find position of 5 accordingly to it as 120 and 180 are multiple of 5. Then 4 left in second column to make 180. To make 56 and 21, 7 will be placed in 3 row n last column. So 2 left in last row to make it 56 and 3 and 1 will be placed in 2nd n 3rd to make it 21. Placed 3 in second row n 1 in first row. Finally 6 and 8 left to make it 54 and 120.
reply
Solved in 2 mins. I first placed 9. Since 180 and 54 are multiples of 9, no other no is multiple of 9. Then find position of 5 accordingly to it as 120 and 180 are multiple of 5. Then 4 left in second column to make 180. To make 56 and 21, 7 will be placed in 3 row n last column. So 2 left in last row to make it 56 and 3 and 1 will be placed in 2nd n 3rd to make it 21. Placed 3 in second row n 1 in first row. Finally 6 and 8 left to make it 54 and 120.
reply
1vader
Forgot to track the time, a few minutes. Would have been way faster with a pencil, I almost immediately got the idea but I'm not good at keeping track of a bunch of numbers in my head so I took a bunch of time to make sure I didn't just immediately forget what I just figured out again.
reply
Forgot to track the time, a few minutes. Would have been way faster with a pencil, I almost immediately got the idea but I'm not good at keeping track of a bunch of numbers in my head so I took a bunch of time to make sure I didn't just immediately forget what I just figured out again.
reply
education
Solved in 2 mins. Started with 7 for the last square as common for 21 and 56. Then last row 2x4x7 ( 4 in the center as the large number - 180 in the center. Then last column 1x3x7 for 21 (3 in center as larger number -120 in center) Then it was easy 6x9x1 for 54.
reply
Solved in 2 mins. Started with 7 for the last square as common for 21 and 56. Then last row 2x4x7 ( 4 in the center as the large number - 180 in the center. Then last column 1x3x7 for 21 (3 in center as larger number -120 in center) Then it was easy 6x9x1 for 54.
reply
Histori
It took me about 5 minutes to solve it. Seeing as only one of the products was odd, I worked out what 3 numbers could combine to form it. I then figured 9 would need to be involved in one of the bigger if not the biggest product. Then factoring. -
reply
It took me about 5 minutes to solve it. Seeing as only one of the products was odd, I worked out what 3 numbers could combine to form it. I then figured 9 would need to be involved in one of the bigger if not the biggest product. Then factoring. -
reply
Paras
Took -30 sec
Start with 21. As 3-7 = 21, position of 7 is known, and so is 3 and 1. Now we know the places of 9 and 6 too, as 96 isn't divisible by 9. Then it gives us 5 and 4 for making the number 180. Rest 8 and 2 would complete the set
reply
Took -30 sec
Start with 21. As 3-7 = 21, position of 7 is known, and so is 3 and 1. Now we know the places of 9 and 6 too, as 96 isn't divisible by 9. Then it gives us 5 and 4 for making the number 180. Rest 8 and 2 would complete the set
reply
JOOT
I solved it without using the rule -use all the numbers 1-9- (because i paused it before the rule came up)
I came up with a different answer but i think its harder that way. The rule just helps you narrow down the answer
reply
I solved it without using the rule -use all the numbers 1-9- (because i paused it before the rule came up)
I came up with a different answer but i think its harder that way. The rule just helps you narrow down the answer
reply
sri
Within 2 mins
3rd column, chose 21, 7-3-1
Then 3rd row
With 7-4-2
Then put 5 in the mid
Then found the left 4 numbers
8-5-3 fit for the second row
Then made the remaining possibilities
reply
Within 2 mins
3rd column, chose 21, 7-3-1
Then 3rd row
With 7-4-2
Then put 5 in the mid
Then found the left 4 numbers
8-5-3 fit for the second row
Then made the remaining possibilities
reply
Jagannath
find the prime factors we get 2, 3, 5, 7, easy to place 7 at the intersection of 21 & 56; 5 is prime factor for 120 and 180 hence goes in the center intersection. rest can be easily worked out
reply
find the prime factors we get 2, 3, 5, 7, easy to place 7 at the intersection of 21 & 56; 5 is prime factor for 120 and 180 hence goes in the center intersection. rest can be easily worked out
reply
Friend
I have been teaching my 5th grade grand daughter how to do these. I found easiest way to teach her is to have her create these puzzles for me to solve so that she understands the mechanics.
reply
I have been teaching my 5th grade grand daughter how to do these. I found easiest way to teach her is to have her create these puzzles for me to solve so that she understands the mechanics.
reply
Silly
2 minutes, no notes. Started with 5 in the middle because of the 180 and 120 and worked it out from there. The hardest part was remembering where I had placed the numbers.
reply
2 minutes, no notes. Started with 5 in the middle because of the 180 and 120 and worked it out from there. The hardest part was remembering where I had placed the numbers.
reply
Moshe
Solved in less than 2 Minutes, but with a pen and paper.
The short time to solve, is extracted from the decision, where to start from.
Nice problem. Thanks.
reply
Solved in less than 2 Minutes, but with a pen and paper.
The short time to solve, is extracted from the decision, where to start from.
Nice problem. Thanks.
reply
Goran
3 minutes, first I solved 21 row(1, 3, 7, then 56 row(2, 4, 7, and just 5, 6, 8, 9 to put in first square, from second try I have ordered them as well
reply
3 minutes, first I solved 21 row(1, 3, 7, then 56 row(2, 4, 7, and just 5, 6, 8, 9 to put in first square, from second try I have ordered them as well
reply
Danish
It took me around 30 seconds to solve, but if someone would have asked me for an explanation at the same time then i would have confused myself!
reply
It took me around 30 seconds to solve, but if someone would have asked me for an explanation at the same time then i would have confused myself!
reply
Ritik's
Solved in literally like under a minute. maybe got lucky this time- started with 1 row and the same column so yeah did that under a minute
reply
Solved in literally like under a minute. maybe got lucky this time- started with 1 row and the same column so yeah did that under a minute
reply
Civil
It took me 4-5 minutes to solve but coincidentally my approach was exactly the same as yours, even the order of filling the boxes was same
reply
It took me 4-5 minutes to solve but coincidentally my approach was exactly the same as yours, even the order of filling the boxes was same
reply
J.
I took a few minutes to solve this without paper, but I'm not sure that I would describe the puzzle as -easy. - It's just doable.
reply
I took a few minutes to solve this without paper, but I'm not sure that I would describe the puzzle as -easy. - It's just doable.
reply
Sharanabasava
Time: 3 min 28 secs
solving was the easy part keeping track of where i put which number was hard -
nicee puzzle.
reply
Time: 3 min 28 secs
solving was the easy part keeping track of where i put which number was hard -
nicee puzzle.
reply
Bujigh
2 9 3
12 10 1
4 2 7
I started with a 10 in the middle since 120 and 180 and it seems alright this solution as well
reply
2 9 3
12 10 1
4 2 7
I started with a 10 in the middle since 120 and 180 and it seems alright this solution as well
reply
Jo-o
Hardest thing here is to keep track of the numbers in your mind, but that's a great mind exercise.
Thank you for this!
reply
Hardest thing here is to keep track of the numbers in your mind, but that's a great mind exercise.
Thank you for this!
reply
GEEK
Solved in 2 mins. Started with 21.
. Since 21 = 7-3-1. Then the Whole Thing will Follow then.
691 - 853 - 247
reply
Solved in 2 mins. Started with 21.
. Since 21 = 7-3-1. Then the Whole Thing will Follow then.
691 - 853 - 247
reply
Add a review, comment
Other channel videos
