Maths Help

[pinkee]

Can anyone help me with the following please:

The sum of the digits of the square of 49 (2401) is the square root of 49.
It is the first number to have this property ignoring one.

Can anyone tell me what the 2nd, 3rd and 4th numbers are that also have this property?

[bobbinwales]

Should be easy to set up on a spreadsheet starting with 50 then 51 etc

[THECORBYLOON]

On you go then...

[bobbinwales]

No spreadsheet on my phone but will try when I get home!

[tedsgran]

only need consider squ numbers..? 64,81,100,etc?

[roslyn251254]

...484 works 484 x 484 = 234256 ...digits add to 22 squ root of 484 =22

[MTbowels]

I think they are 64, 81 and 100 but I'll happily be corrected.

[JJ109]

625 * 625 = 390625
Sum of digits = 25
square root of 625 = 25

[JJ109]

784 * 784 = 614656
Sum of digits = 28
Square root of 784 = 28

Therefore your answer = 484, 625 and 784

[bobbinwales]

Then 1296

[pinkee]

Thank you. Hopefully those will help me!

[davebro]

jj - How did you figure that out? (as my maths tests used to say "show all your workings"!)

[roslyn251254]

trial and error?

[JJ109]

I used a spreadsheet
In column a placed a 7 in cell A1, in Cell A2 set formula =A1 + 1, copied that down to row 100.
In column b squared column A
In column C squared column B
I was going to right formulae to add the digits, but just glanced down the column C and they were easy to spot mentally adding the digits.

[JJ109]

^^ write

[bobbinwales]

I did it same way using a spreadsheet. I also used a function that sum's the digits of a number. I carried on to 12000 but stopped as the differences seemed to be getting bigger and not showing any sign a coming back toward 0 so maybe 1296 is the biggest

[Peter Pedant]

help !

[Atheist]

I checked out numbers up to 8281 and only found the ones that jj109 reported - 484,625 and 784.
I used Excel, but I'm rusty so it took a bit of fiddling and probably not very elegantly done.

[Peter Pedant]

someone who looks like you atheist must be elegant

I am having a few bottle of squidge on skid row tomorrow - care to join me

best offer all week !

[bobbinwales]

you must of missed mine then Atheist
1296 (square of 36)
1296 squared = 1679616
sum of them digits = 36

[Atheist]

I missed 1296!! Thank you Bob.