# Need help with two math problems

#### duragezic

##### Lifer
The first is I need to list 1-100 in binary. I can figure it out but it'd be a lot easier to have the comp do it and then I can copy them down. I was trying to think of a way to do it on my calculator (I know a little BASIC for my 83+) but I'm too dumb. Is there any quick way to do it on the comp?

Next is I have to find X in this mult problem:

x2 * 7x = 6396

Now theres only 9 numbers to choose from but I need an actual way to figure it out, not just guess and check.

#### mithrandir2001

##### Diamond Member
For the second problem:

x^2 * 7x = 6396
7x^3 = 6396
x^3 = 913.714
x = 9.7037

Usually answers aren't like that so you must have copied the question wrong.

#### yiwonder

##### Golden Member
Ok, binary...
1=1
2=10
3=11
4=100
5=101
6=110
7=111
8=1000
9=1001
10=1010
11=1011
12=1100
13=1101
14=1110
15=1111

See any patterns? If not just plow through it.

I assume x2 is x^2...
x^2*7x=6396
Simplify...
7x^3=6396
Divide by 7...
x^3=6396/7
Take cube root of both sides...
x=9.704 (Rounded to 3 decimals)

Edit 2: Do you understand how binary works?

nm

#### Valhalla1

##### Diamond Member
there is a really slow way if you dont know binary you can use calc.exe to convert base ten to base two..

#### duragezic

##### Lifer
Well I know how to convert to binary but I was just wondering if there was a real quick way to list it with the comp.

As for the other problem, not it's x as in variable in the tens digit in the first part, then x as in a variable in the ones digit.

Um this is extra credit

#### GoldenBear

##### Banned

<< x2 * 7x = 6396 >>

Quadratic formula, assuming you mean x^2.

#### yiwonder

##### Golden Member

<<

<< x2 * 7x = 6396 >>

Quadratic formula, assuming you mean x^2.
>>

He couldn't use the quadratic formula. That's a CUBIC...

#### thEnEuRoMancER

##### Golden Member
(10x + 2)*(70 + x) = 6396

Solve for x.

#### yiwonder

##### Golden Member

<< Well I know how to convert to binary but I was just wondering if there was a real quick way to list it with the comp.

As for the other problem, not it's x as in variable in the tens digit in the first part, then x as in a variable in the ones digit.

Um this is extra credit
>>

Well the first 15 took me very little time. You'll get good at it. Hmmm...I think you might just have to guess and check for the second one as I don't know any other way, but that's not to say one doesn't exist...

Edit: Hey, that above method is pretty smart...I wouldn't have thought about that, but then again, this is a once in a lifetime problem...

#### duragezic

##### Lifer
Nononono. No squaring or to the whatever power. Consider it b then. Its a variable.

b2
7b
-------
6396

What is b and how do I get it other than guess and check is my question.

#### gqstyle09

##### Senior member
for the second problem, if you look at the one's digit 6396, only two numbers multiplied by 2 will give you a 6 (3 and 8), then estimate

32*73 is about 30*70 = 2100
82*78 is about 80*80 = 6400

so the answer has to be 8... i would have done it that way, as for some sort of equation or whatever you could use, i can't help you with that

#### yiwonder

##### Golden Member

<< Nononono. No squaring or to the whatever power. Consider it b then. Its a variable.

b2
7b
-------
6396

What is b and how do I get it other than guess and check is my question.
>>

Look at thEnEuRoMancER's post. That will get it for you. Since the first b is the in the tens place with a 2 in the ones, it can be represented as (10b+2). Same goes for the 7 in the tens and b in the ones, (70+b).

Therefore,
(10b+2)*(70+b)=6396
You do the solving...

Edit: The way gqstyle09 did it uses logic. Sometimes it's good to know how to solve it without using logic just because it won't always be that simple. Oh well, I didn't realize how to do it, so I guess I'm not one to talk...

#### gqstyle09

##### Senior member
yah they're right, so much for that \$35,000 a year edumacation of mines hehehe

Edit: logic is cool

#### duragezic

##### Lifer
Ok so how do I do solve that?

At first I was gonna post this and it was embarassing cause I couldn't think of how to solve it but I tried doing it and asked my bro and he couldn't think of how to solve it either.

So it might still be easy but I just can't think of what to do. I think the solver on my calc does it but I don't know how to work the solver.

edit: yes I know how binary works at least I did a couple days ago I might have to just take a quick look at my notes to refresh my memory though. I'm trying to do it on my calc but it'll take me longer to do that but it'll be cool if I did cause I'd be l33t but I'll just do it normally I guess.

#### duragezic

##### Lifer
^^^ im a friggin idiot and I need to get this soon I'm tired I didn't accomplish anything today though I suck.

#### yiwonder

##### Golden Member
(10b+2)*(70+b)=6396
Ok, multiply it out.
700b+10b^2+140+2b=6396
10b^2+702b+140=6396
10b^2+702b-6256=0
Now, use the quadratic formula or factor if you have a TI-89, which I doubt you do.
I'll just factor it since it's easier for me (since my calculator can factor). If you need me to do the quadratic formula, then PM me to tell me and I'll post it in the thread.
2(b-8)(5b+391)=0
Therefore, solve for b.
b-8=0 | 5b+391=0 Now, this is a possible answer, but must be thrown out as you are looking for integers only.
b=8

82*78=6396.

See, it works.

#### duragezic

##### Lifer
Ok thanks. I figued I had to FOIL it but I wasn't sure what to do after that. It makes sense now. Thanks.

Thanks to all.

That damn binary shat too longer than I thought. My teacher said 5-10 mins but it took me like 20-25min and it's worth like 5pts. :|