Math Central - mathcentral.uregina.ca
Quandaries & Queries
Q & Q
. .
topic card  



list of
. .
start over

6 items are filed under this topic.
Multiplication and repeated addition 2016-11-23
From Anandmay:
Hello I was looking closely at early arithmetic where I found how we discovered properties of Arithmetic. Like:2 x 3 = 3 x 2. This can be proved by considering a 2-D figure(actually,quadrilateral) having length consisting of 2 boxes of 1-by-1 dimensions and breadth of 3 boxes of the same dimensions. Now,consider it again,but,this time,length of 3,and breadth of 2 of such 1 by 1 boxes. We now notice that we can fit the 2 types of rectangles formed on each other precisely. So the multiplicative property of commutativity is true for all natural numbers as we can generalize the result(in our mind,for self satisfaction).

Now,can you find me a nice satisfactory reason of why a fraction times a natural number equals the number times the fraction? I mean, for example,i can understand the meaning of 3 x 2/3 to be three times 2-3rd,that is, 2/3+2/3+2/3.Fair enough. But here is the problem:By definition and actual meaning of multiplication, a x b means the repeated sum of b,done 'a' times. So what is the meaning of doing 2/3 x 3?The repeated addition of 3 how many times??2/3 times??Not making sense,right?And even we have not proved yet the commutative property of numbers INCLUDING fractions.So how can we resolve this problem and make these things meaningful?

Answered by Penny Nom.
Associative or commutative? 2007-08-24
From Terry:
5*(7*2)=(7*5)*2 Is this associative property or commutative ??? Both?
Answered by Penny Nom.
A binary operation 2007-07-31
From sofia:
Prove that if * is associative and commutative binary operation on a set S, then (a*b)*(c*d) = [(d*c)*a]*b

for all a,b,c,d element in S. Assume the associative Law only for triples as in the definition that is, assume only (x*y)*z = x*(y*z) for all x,y,z element in S.

Answered by Penny Nom.
Binary operations 2007-07-30
From jim:
prove or disprove:

Every binary operation on a set consisting of a single element is both commutative and associative.

Answered by Penny Nom.
A commutative subgroup 2007-05-03
From moulipriya:
If H be a commutative subgroup of a group G. Then can we say that G is also commutative?
Answered by Penny Nom.
Definitions 1997-09-08
From SohoGirl13:
I am an 8th grader. my e-mail address is SohoGirl13@aol.com. I have a question: what are the associative, communitive, and distributive properties?
Answered by Harley Weston.



Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.



Home Resource Room Home Resource Room Quandaries and Queries Mathematics with a Human Face About Math Central Problem of the Month Math Beyond School Outreach Activities Teacher's Bulletin Board Canadian Mathematical Society University of Regina PIMS