algorithms

mcheytan

Junior Member
Joined
Jan 25, 2008
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51
How do I solve this equation?

What number is the equation closest to:

(10^8 - 10^2)/(10^7 - 10^3)

the answer is 10.
i worked it out a little: (10^2)^4-10^2 and 10(10^2)^3-10^2
I don't know how to do it without calculator...
 
mcheytan said:
How do I solve this equation?

What number is the equation closest to:

(10^8 - 10^2)/(10^7 - 10^3) ~ 10[sup:mubrc68p]8[/sup:mubrc68p] / 10[sup:mubrc68p]7[/sup:mubrc68p] = 10
 
mcheytan said:
What number is the equation closest to:

(10^8 - 10^2)/(10^7 - 10^3)
This is not actually an equation (since there is no "equals" sign), and, by nature of the real numbers, there is no one number "closest to" this value, other than the value itself. So the exercise statement makes very little sense.

Your subject line refers to "algorithms". I would guess that this means that you were given some algorithm by which to evaluate or approximate the expression. If this is correct, kindly please reply with this information, along with a clear listing of what you have tried so far. If, on the other hand, my guess is incorrect: my apologies.

mcheytan said:
the answer is 10.
Actually, one closer value would be 10.001, so your book must have something specific in mind. For us to know what that is, you will need to provide us with the rules, assumptions, and/or other information under which you are operating.

mcheytan said:
I didn't understand the previous post.
Have you not studied exponent rules yet...?

When you reply, please be complete. Thank you! :D

Eliz.
 
(10^8 - 10^2)/(10^7 - 10^3)

\(\displaystyle \frac{10^8 - 10^2}{10^7 - 10^3} = \frac{10^2(10^6 - 1)}{10^3(10^4 - 1)}\) and of course 10^6 - 1 is real close to 10^6 and 10^4 - 1 is real close to 10^4, so you might just disregard the "-1's" and simplify from there.
 
Hello, mcheytan!

I found a devious approach . . .
. . Maybe you can scare your teacher . . . LOL!


\(\displaystyle \text{What whole number is the expression closest to? }\;\frac{10^8 - 10^2}{10^7 - 10^3}\)

\(\displaystyle \text{The answer is }10.\)

\(\displaystyle \text{Factor: }\;\frac{10^2\overbrace{(10^6 - 1)}^{\text{diff. of cubes}}}{10^3\underbrace{(10^4-1)}_{\text{diff. of squares}}}\)

\(\displaystyle \text{Factor: }\;\frac{10^2(10^2-1)(10^4+10^2+1)}{10^3(10^2-1)(10^2+1)}\)

\(\displaystyle \text{Reduce: }\;\frac{10^4+10^2+1}{10(10^2+1)}\)


Here's where it gets "cute" . . .

\(\displaystyle \text{We have: }\:\frac{10^2(10^2 + 1) + 1}{10(10^2+1)}\)

\(\displaystyle \text{Make two fractions: }\:\frac{10^2(10^2+1)}{10(10^2+1)} + \frac{1}{10(10^2+1)}\)

\(\displaystyle \text{Reduce: }\;10 + \frac{1}{10(10^2+1)}\)


\(\displaystyle \text{The fraction is slightly less than }\frac{1}{1000} \:=\:0.001\)

\(\displaystyle \text{Therefore, the value of the expression is close to }10.\)
 
Thank you guys!
Firstly, I did not get first reply to my post, because it just showed my problem and an answer without explanation. I have studied exponent rules 3 years ago and basically i am reviewing now.
Second, the first time I posted the problem this is all complete information I am given, and have to solve it for 2 minutes, without calculator. This is part of GMAT test and I was trying to get the idea/logic to it.

Thanks for the ideas!
 
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