Three Wrongs Make A Right?

Can an odd number, divided by another odd number, times another odd number ever equal an even number?

If "yes," then find three numbers that work. If "no," then why not?

Clarification: The three odd numbers can be different numbers.

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16 solutions

Patrick Engelmann
Oct 27, 2015

No, it can't happen.

Let's first rewrite this equation:

O 1 O 2 O 3 = E \frac{O_1}{O_2} \cdot O_3 = E

O 1 O 3 = E O 2 O_1 \cdot O_3 = E \cdot O_2

O 1 , O 2 O_1, O_2 and O 3 O_3 are all odd and E E is even. This means, we can write them in the following form, where p , m , n , k Z p, m, n, k \in \mathbb{Z} :

( 2 p + 1 ) ( 2 m + 1 ) = 2 n ( 2 k + 1 ) (2p + 1) \cdot (2m + 1) = 2n \cdot (2k + 1) 4 p m + 2 p + 2 m + 1 = 4 n k + 2 n 4pm + 2p + 2m + 1 = 4nk + 2n 2 ( 2 p m + p + m ) + 1 = 2 ( 2 n k + n ) 2 \cdot ( 2pm + p + m ) + 1 = 2 \cdot (2nk + n)

This means: ODD x ODD = ODD and ODD x EVEN = EVEN .

This means again that our equation can never be true

we know '0' is an even number .. so if one number is zero 0/1*3=0 so this results true.. is it the way?

Shibbir Hossen - 5 years, 7 months ago

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it says (odd/odd)*odd=even

you can only use zero on right side of equation where "even"is found how can you use odd numbers and division and multiplication to come up with zero?

Carmelo Mancia - 5 years, 7 months ago

Because 0 is even we cant use it in this case

Sergio Alejandro Acelas Avila - 5 years, 7 months ago

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we can use 0 because it is also even.

Nicko Valero - 3 years, 7 months ago
Chaitanya Lodha
Oct 22, 2015

any no. can be written as the product of its prime factors. an even number is a number having 2 as one of its factors. so all the three no.s in the question don't have 2 as its factors. hence their product or its quotient cannot be even

Pedro Henrique
Oct 27, 2015

I Just used a extremely simple and useful mathematic principle O d d O d d × O d d 1 = E v e n 1 × O d d = E v e n O d d E v e n \frac { Odd }{ Odd } \times \frac { Odd }{ 1 } =Even\\ \\ 1\times Odd=Even\\ \\ Odd\neq Even

although the end statement is correct, I do not think you can use this method because you are implying that odd/odd are the same number. Easy counter example is 3/5 ......the question just ask if this can ever be true, suggesting that odd/odd doesn't have to be the same number

jose Hernandez - 5 years, 7 months ago

Well, it is true that O 1 O 2 O 3 \frac{O_1}{O_2} \cdot O_3 can't be an even number it might not always be an odd number as well. We don't have definition for odd/even rational numbers .

Sachin Sharma - 5 years, 7 months ago

While the answer is correct, an odd number divided by an odd number is not always 1. For example, 3 / 1 follows the Odd/Odd and is not equal to 1.

alex schroeder - 3 years, 4 months ago

The odds can’t be the same number bro. Good try though

Jerry Christensen - 2 years, 7 months ago

Lets take 1 for the odd position,the answer will be 1 which is not even!

via jts - 1 year, 7 months ago
David Heras
Jun 8, 2016

You're doing arithmetic in F 2 × \mathbb{F}_2^\times on the left. Which is closed. The right is not an element of that group, so it is not possible.

Chris Galanis
Oct 28, 2015

Let A , B , C A, B, C be the odd numbers and E E be the even one. A B C = E A B = E C = λ { E = λ C E is even C is odd λ = 2 k ( ) A = λ B ( ) A = 2 ( k B ) ( C o n t r a d i c t i o n ! ) \frac{A}{B} \cdot C = E \Rightarrow \frac{A}{B} = \frac{E}{C} = λ \Rightarrow \begin{cases} E = λ \cdot C \stackrel{\text{C is odd}}{\stackrel{\text{E is even}}{\Rightarrow}} λ = 2\cdot k (*)\\ A = λ \cdot B \stackrel{(*)}{\Rightarrow} A = 2\cdot \Bigg(k\cdot B\Bigg) \rightarrow \text(Contradiction!)\\ \end{cases}

Mycroft Holmes
Oct 27, 2015

If 2 is a factor of the product, then 2 has to be a factor of either the multiplier or the multiplicand. Which is not the case here. One might ask, can (ODD/ODD) yield an even quotient? It cannot. Again, if the quotient is a multiple of two, then the dividend has to be a multiple of 2 too.

If (O1/O2) O3 = E, then, O1/O2 has to be a even number, because (Odd number) (Odd number) = (Odd number).

But if O1/O2 = E, then, O1 = O2 E. Thus O1 is an even number, because (Odd number) (Even number) = (Even number). This is an absurde!

Thus, (O1/O2)*O3 = E can never happen.

From the question " [Odd/Odd] x Odd = Even ". We get Odd x Odd = Odd x Even = Even. (multiply Odd) NONE of Odd number production can give even number. The answer is NO

Jenson Chong
Dec 10, 2020

3x3=9 x X = X= no

it's not right at all.

Didi Pikachiu
Sep 9, 2018

NO! Take the odd number as 1 . 1 1 \frac{1}{1} times 1 is 1 * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! * THE ANSWER IS AN ODD NUMBER!!!!!!!!!!!

Bimol Nath Roy
Feb 6, 2016

No, it can't happen. Cause, When we divide an odd by an odd that will also an odd number. so (Odd/Odd)=always Odd.And multiply of Two odd numbers is also an odd number.(Odd x Odd)=Odd So it can't happen.

Albert Mourato
Oct 27, 2015

Counter example: (21/7)*3 = 9 that is odd.

Mani Shankar
Oct 27, 2015

Genral form of odd is (2n+1) or (2n-1)

so if we take 2n-1 we get (2n-1)/(2n-1)*(2n-1) => (2n-1).. i.e.., Another odd number only.

Ashish Sharma
Oct 27, 2015

Every odd number Is a multiple of 2 odd number If we divide with an odd number the number left is odd and then multiplying it by odd would result odd

Anirudh Vikash
Oct 23, 2015

Because when we divide any odd number by another odd number it will give odd number and multiply will be also an odd number.for e.g. (17/5)*7=an odd no.

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