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Questions tagged [ratio]

For questions concerning the ratio of a certain quantity to another.

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208 views

Calculte new width and height of the video based on the original width, height and ratio

after searching through - I wasn't able to find the answer so I'll give it a shot here. I need to resize desktop video in order to feet it on mobile screen, let's say original width of the video was $...
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2answers
51 views

Playing audio files at lower % of regular speed - how long will they be? negative percentage / ratio calculation

I got a knot in my brain and can't think of this - I'm sure it's quite simple and I'll be like "duh!" once someone points it out to me... So the problem is as follows: An audio file is 30 seconds ...
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1answer
2k views

Determining the ratios needed in gear reduction

I am trying to work out the math behind building a gear box for turning a gear a specific RPM from a small motor. Given that a typical DC hobby motor turning at 200 RPM, and a target in the final ...
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56 views

How many ticks are required to count the following revolution per minute?

The timer in my micro-controller is running at 25Mhz. I need to program the hardware timer such that it counts for 6400 rpm. This means 6400 times on bit '1' in 60 seconds. So in 1 seconds it is 1 ...
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75 views

Temperature relationships (ºC, ºF and ºK)

In a curious exercise I found, I know that the relationship between ºC and ºF can be given by: $$F=\frac95C+32$$ I also know that the relationship between ºC and ºK can be given by: $$C=K-273,15$$ I'...
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39 views

Problem finding quantities given ratios

Every other one seemed straightforward to solve except this. It looks simple but I still can't seem to solve it. A, B and C are mixed according to the ratios A:B = 1:7 and B:C = 13:9. Find A, B and C....
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83 views

Simplify ratio 152:121.6:212.8

How am I supposed to know that I can simplify the ratio by dividing with 30.4? Is that such an obvious common factor? How would you go about this if you had 60 seconds time to solve it? You're ...
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1answer
233 views

Error propagation for ratio data

I'm working with some published ratio data for isotopes of uranium (238U) and lead (208Pb and 206Pb). The data are published in ratios of 238U/208Pb and 206Pb/208Pb, but I need the data to be in the ...
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699 views

Fuel and Oil Ratio Problem

Joel mixes petrol and oil in the ratio 40:1 to make fuel for his leaf blower. (i) He pours 5 litres of petrol into an empty container to make fuel for his leaf blower. How much oil should be added to ...
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1answer
227 views

What is the greek symbol that represents the ratio of the length and with in a rectangle.

I understand that there is pi, but I was provoked by a question that asked this, "I have a rectangle and if I cut a square off of it it produces the same type of rectangle. I know that the width is 1 ...
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1answer
383 views

Normal Ratio Distribution with CDF Method

I think I'm missing something glaringly obvious here that's causing problems for me in the entire subject. I have two independent standard normal random variables, X and Y ~N(0,1), and I need to find ...
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2answers
876 views

Distribution of ratio of uniform and exponential random variables

This is a homework question, I feel like I'm doing it right, but I can't seem to get the answer to match up. I have a uniform RV from 2 to 4, and an exponential with mean 4, so $X \sim \text{UNI}(2,4)...
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Dividing contents with ratios

I'm taking a mock test and there is a relatively straight forward question that I am not sure about. ...
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515 views

Distance and speed of two people walking 100 miles

This is for GRE math prep. Can you explain why the answer to this is 54? ...
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1answer
232 views

Ratios to get the total

How do you solve this question? A cookie jar contains only two types of cookies - macaroons and ginger snaps. The ratio of macaroons to ginger snaps is $2:5$. Which of the following could be ...
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2answers
188 views

Proportions question with ratios

Can you help me understand the answer to this question? ...
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1answer
44 views

Figure out simple joint formula for sets of vectors?

I have on the left side four pairs of sample values that result in the respective pair of values on the right side. ...
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67 views

Express the following in terms of $q$.

Given that $\cos{160^{\circ}} = -q$, express $\cos70^{\circ}$ in terms of $q$. No example in the book, don't know how to do it?? I need a complete explanation.
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140 views

Ratio Math Problem

This is from a competition math problem I had recently that I just couldn't figure out. If $ (x+y):(y+z):(x+z) = 1:2:4$ and $x+y+z=35$ compute the value of x. I can tell that $7*(x+y)=2x+2y+2z$ ...
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269 views

Change in length of a right triangle

And so my question is how do I prove the ??
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66 views

Question regarding ratio

I was trying to prove some of the results related to beta function and I came across this step Therefore, $$\frac{B(m+1,n)}{m}=\frac{B(m,n+1)}{n}=k,\quad\mathrm{say}\quad\ldots(i)$$ This yields ...
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3answers
963 views

Finding a combined ratio from two other ratios

So I have a problem with ratios that I need to sort out. I want to know how much of each of two types of food I need to eat in order to get a fixed amount of protein and carbs. an example... I want ...
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43 views

Uniqueness of Point

I want to proove: For points $P \neq Q \in \mathbb{R}$ and $a,b >0$ there is exactly one point $X \in [PQ]$ and exactly one point $X' \notin [PQ]$ with ratio $a:b$. For $a=b$ there is only one ...
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209 views

Simple ratio problem that I can't solve.

One fifth of criminals are hard-core criminals. The hard-core criminals commit two-thirds of the criminal acts. What is the ratio of the number of criminal acts committed by the average hard-core ...
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86 views

Calculate ratio $\frac{p^{3n}}{(\frac{p}{2})^{3n}}$

How do I calculate this ratio? I do not know even where to begin. $$\frac{p^{3n}}{(\frac{p}{2})^{3n}}$$ Thanks
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47 views

Bound for the Ratio of Standard Normal to Standard Cauchy

Let a(x) = N(0,1) and let b(x) = C(0,1). I would like to prove that the ratio of $$\frac{a(x)}{b(x)} \le \sqrt{\frac{2\pi}{e}}$$ Doing algebraic simplification yield something like $$(1 + x^2)e^{\...
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1answer
203 views

Maintain relationship between two numbers, when their sum equals 1

I have a question that I hope won't seem too silly. I have four numbers that add up to one: A= 0.4 B= 0.3 C= 0.15 D= 0.15 Now, assume that numbers C and D are removed and that I want to maintain ...
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94 views

Ratio and proportion problem

Question: If $$(a+b):(b+c):(c+a)=6:7:8$$ and $a+b+c=14$, then find the value of $c$. My solution: $$\frac{(a+b)(c+a)}{(b+c)}=\frac{(6)(8)}{7}$$$$\Rightarrow \frac{ac + a^2 + bc + ba}{b+c} = \frac{...
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4k views

Avoid dividing by zero with just variables and basic operators

I am working on stats for a sports team, and one of the stats I have the ratio of Shots and Shots on Target (Which I call ...
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2answers
849 views

solve ratio word problem without algebra

Four gallons of yellow paint plus two gallons of red paint make orange paint. I assume this makes six gallons. So the ratio is 4:2, or 2:1. Question: how many gallons of yellow paint, and how many ...
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2answers
1k views

Simple but strange ratio problem, I understand the general case but not for this specific question

There is this ratio question that I understand the general case, but not for this specific case. Problem: A rectangle measures 32 cm by 24 cm. Given that its measurements are increased in the ratio 5 ...
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1answer
161 views

Solving Three Part Ratio

I came across this question today and my Math 20-2 instructor expects that I know how to solve it. I have never seen a ratio like this before, I am usually using a ratio with 2 parts ($a:b = c:d$ or $\...
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168 views

How to interpret the ratios calculation in H. Simon's watchmaker parable?

In 1962 Herbert Simon wrote a paper in which he presents his watchmaker parable about how piecemeal construction is more robust than one-shot construction. I won't repeat the full argument here - see ...
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259 views

Homework help: Ratios in Mathematics [closed]

I'm trying to solve this ratio problem. Can't seem to get around in solving it. $750g$ of salt is to be divided between three storage cans $A, B$ and $C$ in the ratios $A:B = 5:2$ and $B:C = 3:2$. ...
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3answers
45 views

Simple probability of x being in a segment given ratio.

I am new here and I have a question. So, lets say I have a line with points A,B,C,D and it looks like this. I am in precalculus and for some reason I just can't remember how to do it. <-A-----B----...
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68 views

discrete math question for ratio

From n men and n women one wants to select k male and k female candidates, to create either a committee or a ballot. In a ballot the members are fully ranked (first, second, ...); in a committee they ...
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58 views

Ratio Questions

this question is stumping me which is a pain because it was found in a basic high school math book. When a car is moving at 108 km/hr, it travels 18km on a litre of petrol. If petrol costs €1,62 ...
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1answer
110 views

Ratio of vertices to edges when airplaines can fly from 1 of 4 cities to any other of the 4 cities

This is a true of false question: There are direct (nonstop) flights amount four cities that make it possible to get from any city to any other city by air. It follows that the beta index of the ...
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307 views

Can a graph with 3 vertices have a ratio greater than 1 of edges to vertices

A graph with three vertices has a beta index no greater than 1. A beta index of a graph is the ratio of number of edges to the number of vertices. The answer key says true but I think it's false. If ...
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0answers
27 views

Variance of ratios of correlated values

I want to estimate a scaling factor $s$ between two vectors of scalars $a$ and $b$. In the ideal case it would be constant for all components, so $a = s \cdot b$, however there is some noise in the ...
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1answer
100 views

Figuring out the third equation required to solve a three variable problem.

I have tried for more than hour now to solve this one. If $4x^2+9y^2+z^2-6xy-3yz-2zx=0$ and an amount of $\rm Rs.3575/$- is distributed among three persons $\rm A,B,C$ in the ratio $\rm x:y:z$. ...
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390 views

Ratio of balls in a box

A box contains some identical tennis balls. The ratio of the total volume of the tennis balls to the volume of empty space surrounding them in the box is $1:k$, where $k$ is an integer greater than ...
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2answers
4k views

How to calculate negative profit margin?

I sold a pair of shoes last week a \$150.00. The cost is \$100. My profit margin for last week is 33% (Revenue - Cost) / Revenue What if the customer returned the shoes? Is my profit margin $0$ or ...
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1answer
5k views

How to find the ratio of two numbers written in scientific notation, such as $ 2.69 \cdot 10^{-8} $ and $ 2.23 \cdot 10^{-7} $?

The numbers are forces and he wants us to put them in a ratio in order to compare them, but I'm really bad at ratios so. $ 2.69 \cdot 10^{-8} $ Newtons is obviously smaller than $ 2.23 \cdot 10^{-7} ...
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Need help solving a question that includes ratios

Three groups, Group A, Group B, Group C, of Sam's friends decided to buy a watch as a memorable gift for his birthday. They contributed 1200 AED in the ratio of 3:4:5. How much did each group ...
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262 views

Calculating percentage to compensate for percent discount.

Missing something very basic here and cannot pin point it. We need to charge a client \$100 for a product. Let's say our payment processor charges us 10% on every transaction. We make this ...
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1answer
197 views

How does knowing a ratio help me determine a total?

I am working with this question: A received 1/3 more votes than B. Which of the following could have been the total number of votes cast for the two candidates? Answer options are 12, 13, 14, 15, 16. ...
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77 views

Percent spread in ratio

Say I have five solutions of various concentrations such as the below: A = 16% B = 12% C = 12.5% D = 17% E = 5% Their quantities do not matter, only their ...
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162 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 $\frac{a}{c} = \frac{2}{...