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# in interesting math problem

criticaldensity
of sorts...

1.Grab a calculator. (you won't be able to do this one in your head)
2. Key in the first three digits of your phone number (NOT the area code)
3. Multiply by 80
5. Multiply by 250
8. Subtract 250
9. Divide number by 2

sea
interesting... got back my own number... good one!
mOrpheuS
OK...to simplify the trick...
leaving out the remaining part, what we are doing essentially is adding 1 then multipying by 250 and then subtracting 250...that getting us back to square one. (x+1)*250 - 250=250x

multiplying by 80 and then by 250...that's in effect, multiplying by 20000.
ie,
{first 3 digits * 20000 + 2*(last four digits)} / 2 =

first 3 digits * 10000 + last four digits = original number.

hmmm...
Bondings
 mOrpheuS wrote: OK...to simplify the trick... leaving out the remaining part, what we are doing essentially is adding 1 then multipying by 250 and then subtracting 250...that getting us back to square one. (x+1)*250 - 250=250x and about the remaining part... multiplying by 80 and then by 250...that's in effect, multiplying by 20000. ie, {first 3 digits * 20000 + 2*(last four digits)} / 2 = first 3 digits * 10000 + last four digits = original number. hmmm...

And I thought he bewitched my calculator.
It's really an interesting trick!
Conikair
Ooh, I love stuff like that! Very cool.
irish_18
Its very cool! I like it!
tommy.studio
Ya!
It is very cool!
I can use this to play my friends.
Firebolt
Its a very good trick but where do people get all these math things from there has got to be a site for all these things
dan751
Here's an interesting problem to this math problem...
I entered everything precisely as instructed, on my scientific calculator, I got "65703" only 5 digits, and on the calculator on the pc, I got "7423109". The scientific calculator is obviously no where near my home number. And I entered 742-3109 as my home number (I made it up). However, I only got it after the 4th time. The scientific calculator follows BEDMAS.
snowboardalliance
 mOrpheuS wrote: OK...to simplify the trick... leaving out the remaining part, what we are doing essentially is adding 1 then multipying by 250 and then subtracting 250...that getting us back to square one. (x+1)*250 - 250=250x and about the remaining part... multiplying by 80 and then by 250...that's in effect, multiplying by 20000. ie, {first 3 digits * 20000 + 2*(last four digits)} / 2 = first 3 digits * 10000 + last four digits = original number. hmmm...

lol good job at solving that one. I was pretty sure it would show your number, just wasn't sure how exactly it did it.
myrevolt
yeah i tried it on my TI-89 and had the same problem, but, see that's because the calculator is using the order of operations, where as the trick relies on it being in the specified order. remember PEMDAS (Parenthesises Exponents Multiplication, Division, Addition, Subtraction.) just do every step by step rather than all at once. cool trick, i am still trying to figure out the lil gimmick, gimme a sec....

UPDATE: Ok so all that add this, divide this gives you the equation: 10,000*x+y (where x is the first 3 digits and y is the last 4 digits)
completeforums
That's cool, I wonder who figured out that trick.
Thumpercats
That is a neat little trick. Nice job on figuring that one out! I will be sure to go and amaze some people with this trick. It is so simple, yet so interesting.
Arightwizard
This trick was amazing!..Until I read the other post..LOL
Still a neat trick even after 3 years.
ftv_flung
Fantastic, I really like it hahaaaha

I'm gonna pass that one round
Zuex
Lol, thats pretty good, i could work out someones number from just the first few numbers!
Afaceinthematrix
 Zuex wrote: Lol, thats pretty good, i could work out someones number from just the first few numbers! :lol:

You wouldn't need to. You're provided with the phone number already.

I've seen this problem before. It's extremely easy but it has so many steps that it essentially confuses and impresses many people.

2. Key in the first three digits of your phone number (NOT the area code)
3. Multiply by 80
5. Multiply by 250
8. Subtract 250
9. Divide number by 2

Steps 4 and 8 pretty much cancel each other out. Steps 3 and 5 multiply to 20,000. Step 9 cancels out step 7 and outs the 20,000 to 10,000. So all you're doing is multiplying the first three numbers by 10,000 and then adding the last for so that you get the phone number. XXX turns into XXX0000 and then when you add YYYY you get XXXYYYY.
carlospro7
obviously this math trick can be broken down, and it's not a magic trick, but it's a pretty cool trick
jhamz
cool one......
blackfish
wow. that was pretty lame.