Questions on fractions, numbers of the form $p/q$ where $p$ and $q$ are integers, and $q$ is not zero.

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1
vote
1answer
35 views

Simplifying an expression written as the sum of three fractions

Specifically, I don't know what to do first given the following expression: $$ \frac{4x - 2}{6} - \frac{2 - x}{4} + \frac{x + 3}{3} $$ So I think of it as $\frac 16(4x-2) - \frac 14(2-x) + \frac ...
-4
votes
1answer
43 views

what would be the answer [on hold]

The average of $3$ numbers is $14$ and the smallest of these numbers is $10$. If one of the other two numbers is $8$ less than the other number, which of the following equations represents the ...
0
votes
1answer
17 views

How to label a tenth of a second properly in a graph?

I'm making a graph for a science class, and the x-axis represents every tenth of a second. What's the best way of labeling that axis other than "time (one tenth of a second)", or is that the best way? ...
2
votes
1answer
21 views

Finding the limit by factoring the denominator and canceling

I have the problem $$\lim_{x\to10} \frac{x-3}{x^2+7x-30}$$ If I factor it to $\dfrac{x-3}{(x+10)(x-3)}$ then $x-3$ cancels and I'm left with $0$. I know the real answer is $1/20$, but why is zero ...
0
votes
2answers
75 views

Parametric solution of the Diophantine equation $\frac{1}{p}=\frac{1}{x}+\frac{1}{y}+\frac{1}{z} ,x,y,z∈Z^+.$

I have prove that, for any given positive integer $p,$ parametric solution of the Diophantine equation $$\frac{1}{p}=\frac{1}{x}+\frac{1}{y}$$ can be written in the form $x=ac(a+b),y=bc(a+b),$ where ...
34
votes
6answers
758 views
3
votes
2answers
54 views

Show that $\frac 1{1+x+y^{-1}}+\frac1{1+y+z^{-1}}+\frac1{1+z+x^{-1}}=1$ if $xyz=1$

If $x.y.z=1$ show that $\dfrac 1{1+x+y^{-1}}+\dfrac1{1+y+z^{-1}}+\dfrac1{1+z+x^{-1}}=1$ My attempt - L.H.S$=\dfrac 1{1+x+y^{-1}}+\dfrac1{1+y+z^{-1}}+\dfrac1{1+z+x^{-1}}$ $=\dfrac y{y+xy+1}+\dfrac ...
1
vote
3answers
28 views

Show that $\frac{(b+c)^2} {3bc}+\frac{(c+a)^2}{3ac}+\frac{(a+b)^2}{3ab}=1$

If $a^3+b^3+c^3=3abc$ and $a+b+c=0$ show that $\frac{(b+c)^2} {3bc}+\frac{(c+a)^2}{3ac}+\frac{(a+b)^2}{3ab}=1$
-2
votes
4answers
130 views

Canceling in fractions sometimes gives a wrong result

When the same factor appears in the numerator and denominator, it can be canceled out: $$\frac{4a}{4a} = 1$$ However, in this more complicated fraction this does not work: $$\frac{4ac-b^2}{4a} \neq ...
0
votes
1answer
37 views

Could this be factored any further?

My friend recently told me that $\frac{-x}{x}$ could not be simplified any further. Is he correct or could it be simplified such that the answer isn't undefined when you ...
3
votes
1answer
172 views

How do I prove that any unit fraction can be represented as the sum of two other distinct unit fractions?

A number of the form $\frac{1}{n}$, where $n$ is an integer greater than $1$, is called a unit fraction. Noting that $\frac{1}{2} = \frac{1}{3} + \frac{1}{6}$ and $\frac{1}{3} = \frac{1}{4} + ...
0
votes
2answers
20 views

Using a factor tree to reduce a fraction? Good Idea?

I am trying to figure out how one reduces 180/100 to 9/5 My factor tree for 180 is 90 *2 - 30*3 -5*6 - 2*3 Thus my prime numbers are 2*3*5 = 30 Maybe I have totally forgotten how to reduce a ...
3
votes
1answer
35 views

How to go from 1/6 to 16 2/3

A VCR is programmed to record a TV show that lasts for a half hour. If the cassette tape used can accommodate 180 minutes of programming, what percent of the tape is used for this recording? I did ...
0
votes
1answer
56 views

$\frac{x}{y} \ge \frac{a_1}{b_1} \ge \frac{a_2}{b_2}$ and $b_1 \le b_2 \implies \frac{x+a_1}{y + b_1} \ge \frac{x+a_2}{y + b_2}$?

Given $\frac{x}{y} \ge \frac{a_1}{b_1} \ge \frac{a_2}{b_2}$, where $x,y,a_i,b_i$ are positive numbers. I would like to prove the following: Claim: If $b_1 \le b_2$, then $\frac{x+a_1}{y + b_1} ...
0
votes
1answer
13 views

Doing wrong in this fraction simplification?

$$ \frac{5}{2x-3} - \frac{3}{(2x-3)^2} $$ I have to simplify So I had the minimun common multiple in $$(2x-3)^2$$ which is $$(2x-3)(2x-3)$$ Then I divide the first fraction denominator by my ...
0
votes
1answer
30 views

Integration with partial fractions help please

I'm trying to work in my partial fractions chapter and some were easy but for whatever reason, I'm stuck now: ∫ (x-3) / (x2+2x+4)2 What I tried: since my denominator is of higher order and a ...
1
vote
2answers
32 views

How do I convert a fraction in base 10 to a quad fraction (base 4)?

I am totally confused when it comes to converting fractions or floating point numbers to a different base. I have no problem converting whole numbers to any base but when it comes to fractions or ...
0
votes
2answers
15 views

Simplifying algebric terms

I would like to clarify - when the equation was simplified by dividing both side by 61. why wasnt this equation instead a = 10/61 * b/61 + 230/61 61a = 10b + 230 a = 10/61b + 230
18
votes
1answer
564 views

Simplify $\left({\sum_{k=1}^{2499}\sqrt{10+{\sqrt{50+\sqrt{k}}}}}\right)\left({\sum_{k=1}^{2499}\sqrt{10-{\sqrt{50+\sqrt{k}}}}}\right)^{-1}$

Simplify $$\frac{\displaystyle\sum_{k=1}^{2499}\sqrt{10+{\sqrt{50+\sqrt{k}}}}}{\displaystyle\sum_{k=1}^{2499}\sqrt{10-{\sqrt{50+\sqrt{k}}}}}$$ I don't have any good idea. I need your help.
4
votes
1answer
86 views

Prove that if $\frac{x+y}{3a-b}=\frac{y+z}{3b-c}=\frac{z+x}{3c-a}$ then $\frac{x+y+z}{a+b+c}=\frac{ax+by+cz}{a^2+b^2+c^2}$

If $\displaystyle\frac{x+y}{3a-b}=\frac{y+z}{3b-c}=\frac{z+x}{3c-a}$ then prove that $\displaystyle\frac{x+y+z}{a+b+c}=\frac{ax+by+cz}{a^2+b^2+c^2}$ I tried to prove this in many ways. First, I tried ...
-1
votes
1answer
20 views

Simplify the numerical expression [closed]

9 1/3-12 1/2+(-4 1/6)-(-1 1/6) Simplify the numerical expression
35
votes
1answer
749 views

Why does this ratio of sums of square roots equal $1+\sqrt2+\sqrt{4+2\sqrt2}=\cot\frac\pi{16}$ for any natural number $n$?

Why is the following function $f(n)$ constant for any natural number $n$? $$f(n)=\frac{\sum_{k=1}^{n^2+2n}\sqrt{\sqrt{2n+2}+{\sqrt{n+1+\sqrt ...
0
votes
2answers
25 views

multiply fraction with what number to get a whole number?

I'm solving some programming puzzle and it has come down to this: I've a fraction, say 12/13, and I need to multiply it with a smallest possible natural number (say x) to get a whole number. How do I ...
6
votes
3answers
195 views

Why do these fractions give $99…9$?

Today, as usual, we were doing all those boring numerical computations in our calculators. It all started when my professor replaced $0.2$ with $1/5$. I got into calculating the unit fractions one by ...
0
votes
1answer
19 views

Solving $\frac12 (3y+2)-\frac58=\frac34y$ for $y$ using LCD method

I am solving $$\frac12 (3y+2)-\frac58=\frac34y$$ for $y$ using LCD method. Can't figure out what I did wrong! The answer in the back of the book is $-1/2$. PS: In the first line that is a $1/2$ in ...
0
votes
4answers
69 views

Is $\frac{4x + 2}{12 x ^2}$ simplifiable?

I'd like to know what methods can I apply to simplify the fraction $\frac{4x + 2}{12 x ^2}$ Is it valid to divide above and below by 2? (I didn't know it but Geogebra's Simplify aparantly does ...
0
votes
1answer
31 views

How can I find $x$, $y$ values for $\frac{(1+i)x-2i}{3+i}+\frac{(2-3i)y+i}{3-i}=i$

$$ \frac{(1+i)x-2i}{3+i}+\frac{(2-3i)y+i}{3-i}=i $$ I believe the format I need in order to solve this problem should be such that the real parts and imaginary parts are separated, ...
3
votes
2answers
782 views

How do I get the integer part of a number by using basic arithmetic?

While it is trivial to simply remove the fractional part of an irrational or rational number, and in programming I could just use the floor() or ...
0
votes
3answers
66 views

Divison of Fractions

Intuitively answer of $(1/1)/(1/(5^{-2}))=25$ But assuming this mathematical logic of evaluating $(a/b) /(c/d) = (a*d) / (b*c)$ equation evaluates to $1/25$. Is there any specified rule to put ...
2
votes
3answers
71 views

Simplifying nested/complex fractions with variables

I have the equation $$x = \frac{y+y}{\frac{y}{70} + \frac{y}{90}} $$ and I need to solve for x. My calculator has already shown me that it's not necessary to know y to solve this equation, but I ...
0
votes
2answers
29 views

Simplifying Fractions with Radicals

How would I simplify a fraction that has a radical in it? For example: $$\frac{\sqrt{2a^7b^2}}{{\sqrt{32b^3}}}$$
3
votes
1answer
93 views

How can I do this? $\int\frac{dx}{x^4+1}$ [duplicate]

I tried to integrate this: $\displaystyle\int \dfrac{dx}{x^4+1}$ I tried to do it with the partial fractions method (after factoring the denominator), but the process is really large, and I got a lot ...
4
votes
4answers
510 views

What is the non-trivial, general solution of these equal ratios? [closed]

Provide non-trivial solution of the following: $$\frac{a}{b+c}=\frac{b}{c+a}=\frac{c}{a+b}$$ $a=?, b=?, c=?$ The solution should be general.
1
vote
4answers
163 views

Can a fraction be simplified like this?

Ridiculously embarrassing question, but can $\frac{x^2-x}{x^2-25}$ be simplified to simply $\frac{1-x}{1-25}$? Full thought process here is that this is essentially $\frac{x*x-x}{x*x-25}$ so the $x$s ...
26
votes
14answers
5k views

Logic behind dividing negative numbers

I've learnt in school that a positive number, when divided by a negative number, and vice-versa, will give us a negative number as a result.On the other hand, a negative number divided by a negative ...
0
votes
0answers
30 views

Comparing Fractional Numbers

Does a formula exist for comparing two fractional numbers, without resolving to using anything other than integers and fractions? (Thus not real numbers). In other words: given $\dfrac{a}{b}$ and ...
0
votes
4answers
85 views

breaking up fractions

I have these two fractions ${11 \over 31 }+{-11 \over 61}$ Adding them gives $330 \over 1891$ But how do I go back to the two fractions, once I've added them? I can get the denominators just by ...
0
votes
1answer
30 views

Spending fraction of salary

I have this question and kind of confused... Mary spent $1/4 $ of her salary in for rent and $1/4$ more than rent for car payment. Which of the following could be the fraction of her savings if ...
3
votes
3answers
87 views

How to combine ratios? If $a:b$ is $2:5$, and $c:d$ is $5:2$, and $d:b$ is $3:2$, what is the ratio $a:c$?

How would I go about solving this math problem? if the ratio of $a:b$ is $2:5$ the ratio of $c:d$ is $5:2$ and the ratio of $d:b$ is $3:2$, what is the ratio of $a:c$? I got $a/c = 2/5$ but that is ...
4
votes
3answers
83 views

Ratios as Fractions

I’m having trouble understanding how fractions relate to ratios. A ratio like 3:5 isn’t directly related to the fraction 3/5, is it? I see how that ratio could be expressed in terms of the two ...
2
votes
4answers
54 views

Simplify $\frac{x}{c} - \frac{x}{c-d}$

There's a long time that I don't solve questions like this one. I'm having problems to simplify this one: $$\frac{x}{c} - \frac{x}{c-d}$$
2
votes
1answer
77 views

Is there a mathematical concept of fractions using transfinite numbers as numerators and denominators?

http://de.wikipedia.org/wiki/Cantors_erstes_Diagonalargument (German) http://en.wikipedia.org/wiki/Cantor%27s_diagonal_argument (English) While looking at Cantors method of proof, which he used to ...
0
votes
1answer
44 views

how to tell a fraction in denominator or numerator should be substituted with its integer equivalent

Suppose we have equations as follows (A, C and B are all integers and $\gcd$=greatest common divisor). $$R_1 = \frac{A\times C}{B} \hspace{2cm} R_2 = ...
3
votes
3answers
122 views

What is $\lim_{n \to \infty} \sum_{x=0}^{n-1} \frac{n-x}{n+x}$?

These are two little questions that came to mind while I was looking at this problem. What is $\displaystyle \lim_{n \to \infty} \sum_{x=0}^{n-1} \frac{n-x}{n+x}$? I am fairly certain that the ...
19
votes
2answers
1k views

Why is the decimal representation of $\frac17$ “cyclical”?

$\frac17 = 0.(142857)$... with the digits in the parentheses repeating. I understand that the reason it's a repeating fraction is because $7$ and $10$ are coprime. But this...cyclical nature is ...
8
votes
1answer
397 views

IMO 1979 problem

The question is $$\text{If }\, p, \ q\in \mathbb{N}, \;1-\frac12+\frac13-\frac14-\dotsb-\frac{1}{1318}+\frac{1}{1319}=\frac{p}{q}.\qquad \text{Prove that } 1979\mid p.$$ So my solution went like ...
3
votes
4answers
99 views

Why does $\dfrac{8}{\frac{8\sqrt{145}}{145}} = \sqrt{145}$?

I can't seem to work out why this is true: $$\frac{8}{\dfrac{8\sqrt{145}}{145}} = \sqrt{145}$$ Could someone break it down for me?
5
votes
3answers
334 views

Recognizing the sequence 1/16, 1/8, 3/16, 1/4, 5/16, …

What is the missing number? $$\frac{1}{16}, \frac{1}{8}, \frac{3}{16}, \frac{1}{4}, \frac{5}{16}, \ \ \ [?]$$ $$A. \frac{5}{4}\quad B. \frac{3}{4}\quad C. \frac{5}{8}\quad D. \frac{3}{8}$$ ...
3
votes
4answers
111 views

Deeply confused about $\sqrt[5]{a^5}=(a^5)^{1/5}$

So is this correct? $\sqrt[5]{a^5} = \left(a^5\right)^{\frac{1}{5}}$ I need proof why $\left(a^5\right)^\frac{1}{5}$ can or cannot just be $a^\frac{5}{5}$ or just $a$? I think of that rule of ...
0
votes
2answers
77 views

How does $\sqrt {\frac{{4 + \sqrt {15} }}{8}} = \frac{{\sqrt {8 + 2\sqrt {15} } }}{4}$

I have the follow answering to a question from my textbook: $\sqrt {\frac{{4 + \sqrt {15} }}{8}}$ However my textbook simplifies it to: $\frac{{\sqrt {8 + 2\sqrt {15} } }}{4}$ I've checked and my ...