Another maths problem for you.

Grandonion · Posted: Mon Jan 22, 2007 5:37 pm Post subject: Another maths problem for you.

25² anyone? yup 625 (if you don't get that, you shouldn't be here)
alright then
35² yup? a bit longer but you got there? 1225?, correct
45² 2025?
55² 3025?
65² 4225? keeping up? come on! i'm only 15, i did this almost imediately!

125² 15625? yes it is

can you spot a pattern? at all?

Tell me how it works, and show me the algerba!

If you can, i will be impressed.

Impress me

du5k · A-Source Staff Joined: Nov 05, 2005 Posts: 6357

The idea is to add 200, then add 400, then 600... etc etc

Provided x²=y, where x = (multiple of 10) +5

The formula for this trick is

[ { [(x+5)/10] {[(x+5)/10]-1} (200) } / 2 ] + 25 = y

KiaraSota · Posted: Wed Jan 24, 2007 3:27 pm Post subject:

Dusk has already shown us how to do this kiwi, lol.

0_o wait....how come your on here kiwi?!?!

When did you join Anime Source??? How come you didn't say? Gack...you should go make yourself an introductory thread. Never mind...

Anyway I can understand the reasoning and logic behind the answer made by Dusk, but I couldn't make an answer, hahhah. Well, the regulars of AS will save us all! cue Guardian Angel of AS, lol
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Grandonion · Posted: Wed Jan 24, 2007 5:37 pm Post subject:

First of all well doen to the first one, not the correct or original way of doing it, but works,
Second, nat, if you want to talk to me there are other ways of doing it apart from here

Thridly the trick to doing it quickly is

35²------ asuming that x=3

x times x-1 = 12

5² = 25
put them together 1225

this works with all fo them, very handy

du5k · A-Source Staff Joined: Nov 05, 2005 Posts: 6357

Hey dun double post... or someone will have to unleash a ultimate skill upon you. (WRATH OF THE MOD)

ok.. hey kiwi... You said write out the formula, what you did is a trick, is not a formula... in mathematical terms you need to write out an equation for it to be a formula....

edit> You mean X time X+1, not X time X-1
After I took another look at it... my formula means the same thing

-___-

Grandonion · Posted: Thu Jan 25, 2007 3:40 pm Post subject:

Yeesssss i knoowwww it's a trick, but there is a neat piece of algerba to explain WHY it works, and please don't say kiwi in such spite Cool

KiaraSota · Posted: Thu Jan 25, 2007 4:36 pm Post subject:

But, the nickname kiwi suits you! You are still quite green ^_^ lol. Anyways, they only said it 'cuz I did...all my fault, heehee. Unless you wanna be called kirry chan instead Cool

_________________
"My honesty hurts, more than the lies you told me,
But sometimes only liars can be kind."
This is what you told me as you closed your eyes.
The simple sadness of losing you is overwhelming,
But I'm waiting for you, in a world without you.

xnosferatuxx · newbie! Joined: Jan 29, 2007 Posts: 3

ok.....i dont understand

du5k · A-Source Staff Joined: Nov 05, 2005 Posts: 6357

xnosferatuxx> it not good to post something so short... or the mods will get you

onizukapwns · Yari Ashigaru Joined: Jul 15, 2004 Posts: 247 Location: 42

Grandonion · Posted: Mon Feb 12, 2007 2:53 pm Post subject:

well considering you are 18 and doing a calculus thingy i would expect you to be able to work it out fairly easily, but you'll find the average adult is stumped from it.
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So I hid valently

yunho534 · Posted: Fri Jun 22, 2007 1:37 pm Post subject:

15²=225
25²=625
35²=1225
45²=2025
55²=3025
65²=4225
75²=5625
85²=7225
95²=9025

You square the 5, which makes it 25.
You square the number in the tens place, then add it's own value.
Put the two numbers together.
Ex: 75.
STEP 1: (5)5=25
STEP 2: (7)7=49
STEP3: 49+7=56
STEP 4: 5625
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