Question

how can i prove this a/b∙c/d=ac/ad? this is a theorem. can somebody help me on this pls?

Answer 1

Unless you've copied incorrectly, it can't be proved, in fact it is false. Just test it with some numbers
a=2
b=3
c=5
d=4

a/b x c/d =ac/ad

2/3 x 5/4 = (2x5)/(2x4)
5/6 =5/4 don't think so

Answer 2

Radar, you made a little mistake. On the denominator RHS, you put 2 instead of 3.

Answer 3

I need just reasons to prove that why ac/ad is true about that matter?

Answer 4

You can prove it by inserting in numbers. Radar attempted to that but made a little mistake and came to wrong conclusion.

Answer 5

Inserting mumbers is a good test, not a proof though...

Answer 6

example on this is like this:
if a=b+c then a-c=b
here is the proof:
a+(-c)=(b+c)+(-c) the reason on this is ADDITIVE PROPERTY OF EQUALITY
a+(-c)=b+{c+(-c)} the reason on this is ASSOCIATIVE OF ADDITION
a+(-c)=b+0 the reason on this is INVERSE ADDITION
a+(-c)=b the reason on this is IDENTITY OF ADDITION
a-c=b the reason on this is SUBTRACTION

this is how it goes like !!

Answer 7

Well, you would need to explain my multiplication, division. Dig up that explanation from your notes.

Answer 8

Don't think so, look at the problem as stated at the very top.

Answer 9

RHS is ac/ad according to the post
ac=10
ad=8
ac/ad=10/8=5/4 which is not 5/6

Answer 10

He wants to prove that (a/b) x (c/d) =(ac/ad) which also is c/d (the a cancels)

Answer 11

I just can't see it, and your proof is good for what its proving, but it doesn't relate to the problem as stated.

Answer 12

OK, sorry, Radar, it seems Candice made a mistake in writing down the problem.

Answer 13

I was thinking the same thing in fact I mentioned that in the first post. No problem. I realize testing with numbers does not prove, but if it were true, I would come up with something like a=a (I think you know what I mean)