# Evaluating with fractions

#### collette

##### New member
Hello,
I am trying to help my daughter with homework, I've never had algebra, so I just do the best. I realize this is an easy problem, and I think I am just making it hard and confusing myself. The problem is:
3x
---
5y
for x = 1/5 and y = -1/2

I think I should reduce it to 16/5 * -2/11 getting -32/55, but that just doesn't seem right.
Any help is appreciated.

Thank you!
Collette

#### stapel

##### Super Moderator
Staff member
You have:

. . . . .(3x)/(5y)

You are evaluating at x = 1/5 and y = -1/2. Then:

. . . . .[3(1/5)] / [5(-1/2)] = [(3/1)(1/5)] / [(5/1)(-1/2)] = [3/5] / [-5/2] = [3/5][-2/5] = -6/25

I have no idea how you got the values 16/5 and -2/11...?

Eliz.

#### collette

##### New member
Hello,
Well, like I said, I don't really know what I'm doing. I'll do my best to explain how I came up with my numbers. Using the examples in the book, I thought I needed to reduce the 3 1/5 and 5 -1/2 to fractions, hence the 16/5 and the -11/2. In the book it shows that the -11/2 is reciprocal and should be flipped, then both fractions multiplied. I had no problems figuring out the expressions that contained only fractions, and was able to check my answer with the given answers in the book, but there were no examples using whole numbers and fractions for me to compare with. I guess I just wasn't getting the idea of reducing, but using your example I understand now. I really appreciate your help!
Thanks again!
Collette

#### stapel

##### Super Moderator
Staff member
The expressions (as posted) are 3x and 5y, not 3 + x and 5 + y. You are multiplying, not adding.

Eliz.

#### Denis

##### Senior Member
Collette, remember this:
(a/b) / (c/d) = (a/b) * (d/c)
In other words, "bring up" the lower fraction in order to multiply, but INVERT it;
example (3 / 5) / (4 / 7) = (3/5) * (7/4) = 12/35

AND: when you see something like "5a", that means 5 times a;
so if a = 7, then 5a = 5 * 7 = 35; tu comprends?

Staff member

#### tkhunny

##### Moderator
Staff member
Was that French or Québécois?

#### stapel

##### Super Moderator
Staff member
Español, señor (o señora?).

Eliz.

#### Denis

##### Senior Member
Babel Fish Translation
In English:
you include/understand
Translate again - Enter up to 150 words
tu comprends
Use the World Keyboard to enter accented or Cyrillic characters.

Hmmm...me not know wat you mean, ma belle Eliz: see above.

"Tu comprends" is pure correct French, TK:
Je comprend
Tu comprends
Il comprend
Now why the "s" if "tu" is beyond me...

Tell ya'll one thing: I was sure happy to switch from French
to English from primary to high school.

#### stapel

##### Super Moderator
Staff member
Denis said:
"Tu comprends" is pure correct French.
Sorry. I'd only heard the phrase in Spanish. My bad.

Eliz.

G

#### Guest

##### Guest
OH MY GOD!!!
"tu comprends?" is french, meaning"do you undersatand?"

and "tu comprendesis Spanish. ALRIGHT!!

god.
seems like im talking to a whole bunch of idiots.

G

#### Guest

##### Guest
See the difference???

comprendes and comprends?

#### stapel

##### Super Moderator
Staff member
beautifull_love101 said:
god.
seems like im talking to a whole bunch of idiots.
Um... no, we aren't the ones who are looking like idiots right now. :roll:

Eliz.

G

#### Guest

##### Guest
im not trying to offend anyone. im just trying to conclude about the whole argument.

#### stapel

##### Super Moderator
Staff member
beautifull_love101 said:
im not trying to offend anyone....
Then kindly stop calling people idiots.

In addition, it probably wouldn't hurt if you learned how to spell, how to punctuate, and how to use proper grammar. And it would likely be appreciated if you would kindly refrain from presuming to correct others, at least until you know what you're talking about.

Eliz.

G

#### Guest

##### Guest
actually its my typing

G

#### Guest

##### Guest
its actually my typing