5 1 × 5 1 5 2 × 5 2 5 3 × 5 3 5 4 × 5 4 5 5 × 5 5 5 6 × 5 6 = 2 6 0 1 = 2 7 0 4 = 2 8 0 9 = 2 9 1 6 = 3 0 2 5 = 3 1 3 6 ⋮
What is the value of 5 7 × 5 7 ?
Bonus: Can you explain why this pattern appears, and when it breaks?
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The comments here discuss both
a.) when the pattern breaks down and why
b.) the fact a similar pattern shows between 4 1 2 and 5 0 2 , except the square number pattern in the 3 rd and 4 th digits is decreasing.
(Think about why these might be true before you read them!)
Note also the following variation: N − n = 2 5 0 0 − 1 0 0 n + n 2 . Thus 4 9 × 4 9 = 2 4 0 1 4 8 × 4 8 = 2 3 0 4 4 7 × 4 7 = 2 2 0 9 4 6 × 4 6 = 2 1 1 6 ⋮
I'm not sure if you have heard of Vedic Mathematics... It constitutes very simple tricks to find Squares of such numbers.
For eg: Take 4 9 . To find 4 9 2 , consider:
Nearest (kind of important number) is 5 0 . So the difference between them is − 1 Subtract 1 from 4 9 , you get 4 8 , now divide it by 2 , which yields 2 4
We subtracted 1 , it's square is 0 1 , joining them we get 2 4 0 1
Another eg: Take 9 6 , say we want to find it's square.
Nearest important number is 1 0 0 , so their difference is − 4 . Subtract 4 from 9 6 , we get 9 2 (But we shouldn't divide it by 2 ))
So we have subtracted 4 , whose square is 1 6
Joining them, we get 9 2 1 6
And for numbers like 5 2 which are greater that 5 0 only difference is we add 2 not subtract and the rest is same, and for numbers like 1 0 2 we add 2 with same procedure.
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@Skanda Prasad - This is very interesting and I've never heard of it! Great method! However, when do you know to divide by two? When you said, "Nearest important number is 1 0 0 , so their difference is − 4 . Subtract 4 from 9 6 , we get 9 2 (But we shouldn't divide it by 2 ))" I don't get why you don't divide by two. Can you explain when and when not? Thanks!
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In the case of ( 5 0 ± n ) 2 , we get ( 5 0 ± n ) 2 = 2 5 0 0 ± 1 0 0 n + n 2 = 1 0 0 ⋅ ( 2 5 ± n ) + n 2 = 1 0 0 ⋅ 2 1 ( ( 5 0 ± n ) ± n ) + n 2 . In the case of ( 1 0 0 ± n ) 2 , we get ( 1 0 0 ± n ) 2 = 1 0 0 0 0 ± 2 0 0 n + n 2 = 1 0 0 ⋅ ( 1 0 0 ± 2 n ) + n 2 = 1 0 0 ⋅ ( ( 1 0 0 ± n ) ± n ) + n 2 . The first formula has a factor 2 1 ; the second formula lacks it.
The essential difference is that in the first case, we must go from a number near 50 to about 25 hundreds; in the second case, from a number near 100 to about 100 hundreds.
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@Arjen Vreugdenhil – Nice one, bro... Thanks for showing this...
I haven't learnt Vedic mathematics properly... I just know very few little tricks of Vedic mathematics. Vedic means the ancient. Ancient indian mathematicians have developed excellent ways to improve arithmetic, algebraic etc skills... they are way easier to do than the normal methods taught at school...
can you explain when the pattern breaks & how to prove that?
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The patter breaks down for ∣ n ∣ ≥ 1 0 . Consider:
5 8 × 5 8 = 3 3 6 4 5 9 × 5 9 = 3 4 8 1 6 0 × 6 0 = 3 6 0 0 ( not 3 5 1 0 0 ) 4 2 × 4 2 = 1 7 6 4 4 1 × 4 1 = 1 6 8 1 4 0 × 4 0 = 1 6 0 0 ( not 1 5 1 0 0 ) The reason is that the term n 2 , which accounts for the last two digits, grows three digits long instead.
The trick can still be used, but with caution. For instance, 6 3 × 6 3 = ( 2 5 + 1 3 ) ⋅ 1 0 0 + 1 3 2 = 3 8 0 0 + 1 6 9 = 3 9 6 9 .
I just tried to multiply 57x57. It didn't work. I think looking for a pattern should work best. My question are: How does the red part of the pattern work? I understood the blue part. I would rate this problem a 7 because I didn't understand the pattern. I got confused after I got the answer wrong. I couldn't understand the pattern.
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What do you mean 5 7 × 5 7 = 3 2 4 9 ? The red part are the perfect squares. 1, 4, 9, 16, ...
By the method provided here: 57 is 50+7. So we add 7 to 57, getting 64. Divide that by 2 to get 32.
Since we added 7, we square that to get 49 and append it to the above 32 to get 3249, which my calculator claims is the correct answer.
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Yah im learning vedic math. It's very easy for multiplying. Very cool! Vedic math focuses more on digits than on adding, which makes it much easier. And Lucia Tiberio, how did you fail at multiplying 5 7 × 5 7 ? When all fails, just multiply it, and you should know how to multiply. This problem is not bad, its just that you can't see the pattern, so I don't see why you should rate this problem a 1 0 7 . In fact, for this problem you didn't even need a pattern, just multiply the two numbers.
Multiply the tens digits to get 25, then add 7 to get 32. These are the first two digits. Then, square the7's to get the last two digits, 49.
(10m+n)^2 = 100m^2 + 20mn + n^2 For this kind of a pattern it is nescessary to have 20mn a multiple of 100.For that the value of m should be 5. When the value of n increaes by 1 the value of 20mn increases by 100,ie the increase of 1 in the hundread's place.Thus the pattern follows for (10x5 + n)'s squares.ie,the no:'s from 51 to 59. As 41 to 49 can be written in the form of 50-n,The squares will be in descending order and there will be a decrease of 1 in hundred's place consistently.This why both are true
5 1 × 5 1 5 2 × 5 2 5 3 × 5 3 5 4 × 5 4 5 5 × 5 5 5 6 × 5 6 = 2 6 0 1 = 2 7 0 4 = 2 8 0 9 = 2 9 1 6 = 3 0 2 5 = 3 1 3 6 ⋮
The pattern is:
In R . H . S , the two digits on the left are consecutive positive integers.
The two digits on the right are consecutive perfect squares.
In this way, 5 7 × 5 7 = 3 2 4 9
If we explicit the case of two digit and consider 3digits. Will it be abide the rule as ypu mentioned? :)
I got 3649- I believe I’m right
First two numbers progress incrementally. The last two add the next sequenced odd number to the previous number. Plus 3 then 5 then 7 then 11 and plus 13 for 49.
Let’s look at 5x5+7=32 7x7=49 =3249 fast solution
If it were consecutive perfect squares wouldn't it go 01, 04, 09, 16, 25, 36? What happened to 16 and 25?
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I have edited the solution.
Using what has preceded .... (56+1)(56+1) = 56 x 56 +56 x 2 + 1 = 3136 + 113 = 3249
I like your solution because despite being the less sophisticated it is the FASTEST, and from a practical perspective the best. If you get there and you're correct your method doesn't matter.
Unless it is your business to do a crap-ton of these and then refinement to an abstract is essential.
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Simplest solution is to reach for a calculator!
Although think the game is to solve without multiplying - its easy to see the number progression in the list.
MS two digits increase by 1 each time 26,27,28,29,30,31 ->32
LS two digits are the multiplication of the two values
51 x 51 => 01
52 x 52 => 02
....
56 x 56=> 36
57 x 57=> 49
Hence answer is 3249
Guess by brain is analog not digital.......
57×57 = 3.249 This pattern appears when we first square the number 50, which equals 2.500. As we keep incrementing the base by 1, we can see this pattern appear until the value of the base equals 60, in which case, 60 squared is 3.600, breaking the pattern (since 3.600 doesn't follow 59²'s 3.481) The reason as to why this pattern appears in the first llace is because of the nature of the number 5. Whenever we multiply a number times 5, we are essentially getting the half of 10 times that number: since 5×3=15 and 10×3=30. Thus when we double a number multiplied by 5, we get the original number times 10. This general rule is the reason for why this pattern appears. If we break up these problems' numbers' units and tens into the form (tens+unit)×(tens+unit), we can showcase what is happening by using the distributive property. For example, let's use 57×57 (or 57²) and break it into: (50+7)×(50×7), and perform the operation using the distributive property; the integers we'll get are: 2.500 + 350 + 350 + 49 = 2.500 + 700 + 49 = 3.200 + 49 = 3.249 What's evident here is the nature of 5 at play. When we multiply 50 times 7 twice, it will be the same as simply multiplying 100 times 7 just once, thus getting 700 + 2.500, leaving the last two digits of the number untainted for us to place our squared unit without it affecting the rest of our number. This happpens to the integer bases from 50 to 59. Since we'll start with 2.500, add the unit x 100 (incrementing the hundreds place by the value of that unit) , and then add the squarr of the unit. Making a pattern of increment in the first half and of exponentiation in the second as the base's value increments by 1. (I thought I had to write this as part of my answer, thus I wrote this on my phone without using images or anything.)
Simply square the first digit, add the tens digits to the product, multiply by 100, and add the square of the tens digit
Broken down:
Ones and tens digits | Thousands digit |
(5 x 5) + 1 | 1 x 1 |
26 | 01 |
Thus, 51 x 51 is 2601
Do the same with 52 x 52
Ones and tens digits | Thousands digit |
(5 x 5) + 2 | 2 x 2 |
27 | 04 |
Thus, 52 x 52 is 2704
Now, try 57 x 57
Ones and tens digits | Hundreds and thousands digits |
(5 x 5) + 7 | 7 x 7 |
32 | 49 |
Therefore, the answer to this question is 3249
31+1=32, the next number increases by odd numbers, 3,5,7,9,1,13....
Square of same number is ab ab=(a a+b)(b*b)
5*5=25 25+1 = 26 1 * 1 = 1 —> 2601
25+2 = 27 2*2 = 4 —> 2704
25+3 =28 3*3 = 9 —> 2809
....
25+ 7 = 32 7*7 = 49 —> 3249
It is always the previous number plus the previous number’s root plus the next number. Like 3136+56+57.
57*57=3249
(31+1)=32
36+13=49 (sum next prime Number)
It happens for two reasons, the process of squaring multi-digit numbers and how adding two 5s together equals 10, with a 0 in the ones place.
57 x57 = first multiply units place 7 ×7 =49 place 9 in the answer in units place and hold '4' .,then cross multiply 5×7 5×7 add both the answers(35+35) =70. Then add'4' to the 70 =70+4 =74 place 4 in the tens place in the answer and hold 7 .then multiply 5 ×5 =25 add 7 that gives 32 ..so total 3249
I look at it as being ultimately based on (A + B)^2 = A^2 + 2AB + B^2. It COULD be used indefinitely, but after you hit 60^2 it would become somewhat less user-friendly
5 * 5= 25, 25 +7=32 -->32
7*7=49 -->49
3249
(7 7)=49 (5 5)+7=32 3249
I can't explain why it appears, but i can tell you that it breaks at 59X59, because 9X9 is 108.
9×9 = 81* It breaks at 60X60 because 10X10 is 100. Same idea though
5 0 2 = 2 5 0 0
Simple Trick , use (5*5)+Unit digit number- for first two digits & and square of unit digit for last two digits
Cpnsider number in series The difference between the numbers in red are odd numbers 3,5,7,9,11. So add 13 to 36 to get 49 57×57=3249
5 5=25 +7 = 32 ,7 7=49 Multiply first digit of both the numbers then add the corresponding number(second number) number which will give your hundreds and thousands place number then multiply the corresponding number the answer of which will be your units and tens place. E.g.: 5 5=25 +7 = 32 ,7 7=49 3249,eureka
4-1=3 9-4=5 16-9=7 25-16=9 36-35=11 incremento di 2 nelle ultime 2 cifre di 1 nelle prime 2
57×57
Solution : 5×5 》: 25 + 7 : 32 》: 7×7 : 49 Answer : 3249
57 X 57 = 64 X 50 (add and subtract 7) + 7 X 7, 64 X 50 = 3200 then add 7 X 7 , 3249 easy way to square any number !
57*57 is obviously 3249 if you include the pattern. You don't really have to do all of that crazy stuff! It is very simple
Find a value of k such that n-k=10p or n+k=10p where we consider n^2. In this case, n=57, we have k=3 so that n+k =60. Now, n^2 = (n+k)(n-k)+k^2. Thus, 57^2 = 60×54+9=10×6×6×9+9=10×36×(10-1)+9=10×324+9=3249.
Since we are square we can write it as (50+n)^2 = (50+n)(50+n) = 2500 + 100n + n^2. so 2500 + 700 + 49 = 3249. Since the number each time is 100n + n^2 to 2500, this means that each time the thousand + hundred value increases by 1 (because of the increase in the hundreds (if it is taken as one 2 digit number)) and the units and tens would be the next square number. This patter will stop at 60 * 60, where the thousands + hundred value will increase by 2 not 1 because the square of 10 is 100 which changes the hundreds value.
This is actually a question:does this apply to other no. Sets?
57 × 57 ; 5 × 5 + 7 = 32 ; 7 × 7 = 49 = 3249 !
I just looked at the first digit of each. Being 5, I multiplied them which makes 25. Since they have a second digit that isn't zero, I added the value of that single digit, then multiplied both of the second digits together while remembering that there are 4 total digits. So, 5x5 = 25, 25 + 1 = 26, 26 + (1 x 1) to the ones place = 2601. It's a bit like solving binomials in your head.
The pattern breaks at 60*60
Think of the first two blue digits as hundreds,since 55 x 55 = 3025, then 56 x 56 = 3 1 00 + 2 5 + 11 = 3 1 3 6 , so 66 x 66 = 4 1 00+ something The second two (red) digits have been increasing by adding the progression of ten odd numbers after 11 , that is 3 6 +13+15+17+19+21+23+25+ 27+29+31 = 256 + 4100 = 4356 ......66 x 66 = 4356 Q.E.D. Try 67 x 67; 4200 + 256 + 33 = 4489 and 67^2 = 4489
Going with the original sequence.... 0 1 + 3 = 0 4 + 5 = 0 9 + 7 = 1 6 + 9 = 2 5 + 11 = 3 6 .. and so on
Of course.when it reaches 60^2. the "pattern" breaks because 3600 is (3500 + 10^2), so it skips the 35 XX entry. If we go downwards from 49^2, 48^2, 47^2....we get 24 01 , 23 04 , 22 09 , 21 16 , 20 25 , 19 36 , 18 49 , 17 64 , 16 81 ,16 00 (1500+ 100 ), 1521 = 1400 + 121
If we use that arithmetic rule, when it gets down to 24^2 we are in partial negative number, i.e., 576 = -100 + 676,( 676 is the sum of all odd positive integers from 1 to 49).
The following is the pattern. ;-
: :
: :
✓ 46*46 = 21 16
✓ 47*47 = 22 09
✓ 48*48 = 23 04
✓ 49*49 = 24 01
✓ 50*50 = 25 00
✓ 51*51 = 26 01
✓ 52*52 = 27 04
✓ 53*53 = 28 09
✓ 54*54 = 29 16
✓ 55*55 = 30 25
✓ 56*56 = 31 36
✓ 57*57 = 32 49
✓ 58*58 = 33 64
✓ 59*59 = 34 81
: :
: :
To solve this question you should calculate , go with the logic, or go through the logic. If you followed any other metjod pls write in comments
Any doubt can be asked Please share your metho in comments
(50+h)^2 =50^2 +2 50 h +h^2
= 50^2 + 100h+ h^2
= 2500+ 100h+ h^2
= (25+h)100 + h^ 2
Thus the pattern 's logic is studied in a glance
We could now find the ways to solve it
Here we can solve in 2 ways
✓ On by seeing the pattern. Which would just be a prediction . We dont know if it is a deliberate one or omtenrional one. Even he deliberate ones have logics
(Or)
✓. (50+7)^2 = 2500+700+ 49. = 3249
Multiply the tens column togethet =5x5=25 then add the units digit eg 56x56 = 5x5 +6=31 (blue digits) then square the units column, as in this example 6x6=36 (red digits). Hence answer to 56x56=3136. I think the pattern falls down when you nit 60x60.
To explain why you have to put the number as a sum of fifty plus n. The formula of the square: ( 5 0 + n ) 2 = 5 0 2 + 2 ∗ 5 0 ∗ n + n 2 . This gives 2 5 0 0 + 1 0 0 ∗ n + n 2 You can see the hundreds rise as n rises. You can see the two first digits correspond to n 2 .
It is always the previous number Plus the root of that number plus the next number. Like 3136+56+57.
Seems to work. Say going from 66 to 67.... 4356 + 66 + 67 = 4489 !! But this is just arithmetic - the question was asking for a pattern :-)
The difference between two consecutive perfect squares is always two greater than the difference between the set of two perfect squares directly previous. If n × n = x n then ( n + 1 ) ( n + 1 ) = n 2 + n + n + 1 = n 2 + 2 n + 1 = y n . 2 n + 1 is the difference. 2 ( n − 1 ) + 1 = 2 n + 1 − 2 proves my statement. The answer is 3249.
The numbers on the right are perfect squares (in order) and the numbers on the left are simply ordered integers starting at 26. The color separation was not necessary to solve this problem, but it would have been much harder to find a solution with ill - defined groupings.
All I did was take the last number from the current and last multiplicands (56 & 57 -> 6 & 7) and added them together (6+7=13) then I took the previous result into two parts 31 & 36. Each new step you just add one to the frist part and add the sum you calculated to the second part and then you just reattach the numbers. So 31+1=32 and 36+13=49; 32 & 49 => 3249. Not a ‘real’ mathematical solution but a solution nonetheless. :)
All squares are equal to the previous square plus the next consecutive odd number after the difference from the previous squares 1x1=1 2x2=1+3=4 3x3=4+5=9 4x4=9+7=16, etc.
The values in red increase by consecutive odd numbers starting from 03 i.e. 01+03=04, 04+05=09, 09+07=16, etc.
The numbers in blue increase by a factor of 01.
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Consider the perfect square,
N n ⟹ N 7 = ( 5 0 + n ) 2 = 2 5 0 0 + 1 0 0 n + n 2 = ( 2 5 + n ) × 1 0 0 + n 2 = ( 2 5 + 7 ) × 1 0 0 + 4 9 = 3 2 4 9 where n ∈ N
In response to Challenge Master's note:
The formula N n = 1 0 0 ( 2 5 + n ) + n 2 is arithmetically true for all n . When n = 1 0 , then 2 5 + n = 3 5 and n 2 = 1 0 0 , which exceed two digits and N n = 3 6 0 0 and the pattern breaks.
When n is negative, ∣ n ∣ is in the reverse decreasing order. Then 2 5 + n = 2 5 − ∣ n ∣ follows the increasing order. But n 2 = ∣ n ∣ 2 follows the decreasing order. The pattern breaks again when n = − 1 0 .