Questions on basic arithmetic, e.g. addition, subtraction, multiplication, division, powers, radicals, etc.

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0
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1answer
11 views

Arithmetic Time and Work related question

8 men can complet a piece of work in 20 days. 8 women can do the same work in 32 days. In how many days will 5 men and 8 women together will complete the same work? All I have is: Men's one day work ...
2
votes
4answers
165 views

Reversing the digits with a subtraction

How many 3-digits numbers possess the following property: After subtracting $297$ from such a number, we get a $3$-digit number consisting of the same digits in the reverse order.
0
votes
1answer
26 views

Why do the denominators of two fractions with numerators $1$ add up to a third fraction that have the special things below?

I found out that the denominators of two fractions with numerators $1$ add up to a third fraction that has the sum in the numerator and the product in the denominator. For example, ${1\over ...
1
vote
1answer
25 views

Calculating with brackets [on hold]

I have the formula MV = -0.05 -5(log11.25-1) = -0.31 . I don't understand the 5 part, how would I put this formula into a spreadsheet (Planmaker) ? Thanks
-1
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1answer
45 views

How to divide by negative numbers? [on hold]

How to divide by negative numbers? Like what is the quotient and remainder when 24 is divided by $-5$ or $-24$ is divided by $5$?
2
votes
2answers
22 views

Why do consecutive triangular numbers in pairs like $6$ and $10$ always add up to a perfect square?

I was a bit surprised by this when I thought of it. Look here: $$001, 003, 006, 010, 015, 021, 028, 036, 045, 055$$$$004, 009, 016, 025, 036, 049, 064, 081, 100$$As you just saw, $15$ and $21$ add to ...
0
votes
1answer
13 views

Polynomial with integer values

I'm looking for a polynomial $P \in \mathbb Q[x]$ with $P(\mathbb Z) \subset \mathbb Z$, with $P \notin \mathbb Z[x]$ I found that $f_n := \frac{1}{n}x(x-1)(x-2)\dots(x-(n-1))$ is such an element. ...
1
vote
2answers
37 views

Can you recommend a book with techniques for solving hard algebra/arithmetic problems?

I'm a university student who never really studied maths in high school (I did the basic courses, but because I'm dyslexic I was to embarrassed to try the harder courses) now I'm getting back into it, ...
0
votes
1answer
28 views

Understanding the Math in Logarithmic Progration on Arduino Code [on hold]

This is the code I am trying to understand. for(int x = 2; x < 100; x = x * 1.5) Generates: 2,3,4,6,9,13,19,28,42,63,94 This is what I understand. x=2 so it starts 2 next its x= 2 * 1.5 so x=3 ...
0
votes
2answers
22 views

what is the default order and direction of operation?

I have a division like this 16/8/4/2 what is the default way to do calculations when the bracket is not specified . Method 1 : Is it correct to go from right to left like [16/ (8 / { 4 / ...
0
votes
2answers
48 views

How many numbers end with $0,2,9$?

The question is very simple: How many positive integers from $900$ and down end with $0,2$ and $9$? I think it is either $270$ numbers or $271$ numbers, but I am not sure which one.
0
votes
1answer
37 views

What do I do after this?

The question goes.. In a recent marathon, $\frac{1}{10}$ of the participants finished in less than $3$ hours. $\frac{1}{3}$ of the remaining participants finished in $4$ hours or less. Out of those ...
-3
votes
2answers
58 views

Fraction help… [on hold]

Two thirds of the passengers on a plane are female. Three- fifth of the female passengers are canadian, one third of the male passengers are Canadian. What fraction of the passengers are Canadian?
0
votes
2answers
28 views

Splitting sum into two sums

Assuming that $f$ is a multiplicative arithmetic function. Let $n_1,n_2\in \mathbb{N}$ with $gcd(n_1,n_2)=1$. Consider the sum $$\large S=\sum_{a\mid n_1n_2}f(a).$$ Can I split the sum $S$ into two ...
2
votes
2answers
61 views

Is there another way to prove $(x-n)^2 = (n-x)^2$

Let's say $n$ is $4$. So, I came up with the solution below. $(x-4)^2 = (x-4)(x-4) = x^2 - 8x + 16$ $(4-x)^2 = (4-x)(4-x) = 16 - 8x + x^2 = x^2 - 8x + 16$ I was wondering if there is another way ...
-2
votes
0answers
23 views

Quantitative reasoning about percentages and graph interpretation. [on hold]

If the average family food basket costs 100 Euros at 2nd Quarter prices, how much will it cost at 3rd Quarter prices? a 95 Euros b 97 Euros c 99 Euros d 101 Euros e Cannot say (What is the formula ...
-3
votes
0answers
38 views

the k bat math question number bases [on hold]

The number 77552 miles on the car odometer of Mr ismail which has only eight numbers on the wheel. He was driving his car to a place 147km away from his house. What number that will be displayed On ...
1
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3answers
56 views

Convert 1-5 Grading Scale to 1-100 Grading System

I am creating a formula in Excel to convert 1-5 Grading Scale to 1-100 Grading System Suppose that I have the following table: 97-100 = 1.00 94 - 96 = 1.25 91-93 = 1.50 88-90 = 1.75 85-87 = 2.00 ...
0
votes
0answers
5 views

Creating a Performance Formula Which Awards Longevity

I have a website where I'm grading user performance on a certain metric. Each year, users can earn a grade of 0-100. However, I'm trying to determine an 'all-time' leaderboard for users which ...
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0answers
58 views

Nine plus ten really does equal 21… [closed]

Well I was watching some vines and this kid responded 21 to "What is 9+10?"Well if you add it normally it's 19 but I tried a few other ways and it was 21 BUT I added a few modifications... Either the ...
3
votes
2answers
127 views

How to simplify this arithmetic expression

I'm trying to simplify: $\left[(\frac{3}{4}\right)^{7}\cdot$ $\left(\frac{3}{4}\right)^{-4}]^{2}$ $\cdot4^5$ The only advance that I have done is $\left[(\frac{3}{4}\right)^{14}\cdot$ ...
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votes
4answers
52 views

24 hours before Wednesday [closed]

I have a procedure scheduled for 11 a.m. on Wednesday. I can't take certain medications for 24 hours, so what time should I be able to take my last dose?
3
votes
1answer
57 views

Proof that $\sum_{i=1}^n{1} = n$ for all $n \in \Bbb Z^+$

It seems obvious that $$\forall n \in \Bbb Z^+, \sum_{i=1}^n{1} = n $$ However, I'm having trouble coming up with a formal proof for this. Given a concrete number like $4$, we can say that ...
3
votes
1answer
92 views

Is it possible to express addition as repeated multiplication?

It is possible (and common when explaining multiplication) to express multiplication of positive integers as repeated addition like this: $$4\cdot5 = 5+5+5+5=20$$ And a general expression would be ...
0
votes
1answer
18 views

equality of two sums

Is $\sum _{t=1}^m \sum _{k=t}^m (a_{k+1}-a_k)b_t$ equal to $\sum _{k=1}^m \sum _{t=1}^k (a_{k+1}-a_k)b_t$? If not, then how to derive equations for temporal difference algorithm in machine learning: ...
0
votes
1answer
62 views

What is the contraposive of this statement?

I have to prove the negation of this statement: $$\forall a,b,c\in\mathbb{Z}{\;if\;a\;|\;b\} $$ But the fact that there is a "and" is very disturbing. I think that I am missing something because my ...
0
votes
1answer
21 views

How to determine significant figures involving radicals and exponents

How do you determine the significant figures for solving equations with radicals and exponents? For example, how do you evaluate $x = \sqrt{4.56^2 +1.23^2}$?
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0answers
30 views

Among 10 packet each having weight 100grams 1 packet is defective and weight is 90 grams. How to find out the defective one in only one measurement?

I have 10 packets of cigars. Each packet consists of 10 cigar and weight of each cigar is 10 grams.So weight of each pack will be 100 grams.But Somehow my friend measures packets of cigars and said ...
0
votes
2answers
23 views

Computing an academic grade when relative weights are changed

My grade is 88.6% (High B) and we get 80%(Assessment Grade) and 10%(Homework). My teacher is now making this 70%(Assessment Grade) and 30%(Homework). I have done all my homework 100% and I've been ...
1
vote
2answers
34 views

How to recognise the digit multiplication, subtraction or addition when checking for divisibility by 7, 11, 13, 17 and 19?

I was studying this page Divisibility by prime numbers under 50 to check for the divisibility by 7, 11, 13, 17, 19 etc. Is there any way to recognise whether to add or sub the given times of unit ...
-6
votes
1answer
68 views

you know root square of -1, what is the larger of the square? [closed]

there is a square ABDC, $BD = \sqrt{-1}$ what is the value of AB=BC=DC=AD?
0
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3answers
47 views

The meaning of dot centered vertically, as in $3\cdot 5$

I just went to a site to practise some maths as I am studying some maths on my OU course in computing and IT and I ran into some symbols that I did not understand The questions were solve ...
-1
votes
1answer
42 views

How to find the formula of S3n? [closed]

I have series $$1+2+3+4+4+3+5+5+6+...$$ if $n \in N$ then the formula of $S_{3n}=...$ Even I'm confused the pattern of the sequence. Anyone can help me? 4 first terms is like natural number, but at ...
0
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0answers
40 views

Are ratio notations always equivalent?

Is there any case where the following ratio notations are not equivalent? For cases where the notations are equivalent, under what circumstances would the first notation be preferred? First ...
3
votes
5answers
61 views

Manually obtainining a list of primes $\leq n$, by using the root of n?

In my abstract math class I learned that if we want to get a list of primes $\leq n$ manually, we have to calculate the root of n, and the floor of that result will be the greatest number for which to ...
0
votes
1answer
27 views

Calculating how much money I spent? (23-73 gives

I'm a very simple person with basic math knowledge. Recently I run into huge problems when calculating how much I spent. Sometimes to calculate how much I spent I do a calculation $final sum - start ...
0
votes
2answers
26 views

Use of arithmetic progression to find the sum of numbers

How can I find the sum of numbers divisible by 3 that are between 1 and 1000 if I don't know how many elements there are in the arithmetic progression?
1
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1answer
20 views

Bézout's identity on a polynome sequence

I'm stuck on an exercise which is split in 3 questions : 1) Prove that : $$\exists (U_n, V_n) \in \mathbb{R}[X]^2 \text{ s.t. } (1-X)^{n+1}U_n+X^{n+1}V_n=1$$ 2) Let $(R_n, ...
1
vote
4answers
141 views

Proving that $p_1p_2\mid n$ iff $p_1\mid n$ and $ p_2\mid n.$

Let $p_1$, $p_2$ be distinct primes. Using the Fundamental Theorem of Arithmetic prove that a natural number $n$ is divisible by $p_1p_2$ if and only if $n$ is divisible by $p_1$ and $n$ is divisible ...
0
votes
1answer
30 views

Dividing by zero the answer is undefined

I know that $\frac{1}{0}$ is undefined. What about $\frac{1}{0}-0.5$ it's undefined as well?
0
votes
1answer
17 views

Covering deficits with values with different weights

SO I have a couple of assessments with specific weights as follows: Assignment 1: 5% => Mark 60% Assignment 2: 5% => Mark 53% Assignment 3: 5% Assignment 4: 5% Test 1: 30% => 47% Test 2: 30% ...
0
votes
1answer
29 views

What can you say about two expressions with same reminder?

I am working on Integer factorization problem and I came to those two interesting expressions: $a,b,c,x$ are non negative integers $a,b < c$ $$\frac{ax + b}{c-x}$$ and $$\frac{ac + b}{c-x}$$ ...
1
vote
1answer
41 views

How and why can it be true that some decimals that sometimes go on forever in base 10 such as $1\over 3$ change to good numbers in base 12?

I've noticed on a math channel on YouTube that some of these decimals from fractions in the decimal system such as $1\over 3$, which equals $0.\overline3$, which goes on forever, doesn't show off this ...
1
vote
3answers
86 views

Which number is higher $2^{600}$ or $3^{400}$?

Which number is higher $2^{600}$ or $3^{400}$ ? I know that the solution is $3^{400}>2^{600}$ bot how to explain that. without using a calculator.
0
votes
2answers
49 views

Converting American to Canadian

Paid \$1012 American for a group of items, which worked out to \$1248.99 Canadian. How do I calculate the conversion rate so I can figure out the total cost Canadian of each item?
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votes
2answers
28 views

Simplify the radical expression [closed]

Simplify the following: $$\sqrt{48 a^2 b^7}$$ All I have so far is 16 I think i forgot how to do this, can anyone help?
1
vote
1answer
32 views

What is the proof-theoretic ordinal of $PA+TI(\epsilon_0)$?

what is the proof-theoretic ordinal for $PA+TI(\epsilon_0)$, where $PA+TI(\epsilon_0)$ is Peano arithmetic where transfinite induction up to $\epsilon_0$ was added? Is it known? Thank you
1
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0answers
6 views

algorithm related to dyadic decomposition

Starting from an integer $n >0$, iterate the two operations of substracting one and dividing by $2$ (when the number is even) until $1$ is reached. Thus when the number is odd we can only substract ...
0
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3answers
52 views

simple question [closed]

How would you say 4,954,000? I forgot
-1
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0answers
24 views

Doubt in precedence of operators. [duplicate]

If I write 11 + 4 * 0 + 1 what will be the answer of this. What is the order of operations and operator precedence for this.