1. Algebra: Multiplication!

I just need some help clearing something up, that i don't quite understand:

2/3 x 18c=2/3 x 18 x c
= 12c
---------------
That's Right, right? But how did i get the 2/3 x 18??? How was i mean't to get 12?
This is out of a example page, when were talking about how any two terms can be multiplyed together!
Can you help me clear this up?

2. Re:

Wait is

"x" a variable or are you trying to multiply? Please specify...

3. Originally Posted by qbkr21
Wait is

"x" a variable or are you trying to multiply? Please specify...
no, apparently "x" is the multiplication sign, c is the variable

4. yeah, um.. What i'm trying to find out is, it says that 2/3 x 18 equals 12... as i wrote:

it shows: 2/3 x 18c= 2/3 x 18 x c
= 12c

5. Originally Posted by Sazza
yeah, um.. What i'm trying to find out is, it says that 2/3 x 18 equals 12... as i wrote:

it shows: 2/3 x 18c= 2/3 x 18 x c
= 12c
we think of this as multiplying two fractions. when multiplying two fractions, we multiply the tops to get the top of the new fraction and multiply the bottoms to get the bottom of the new fraction. but we have the option of reducing things before doing that. if a number in the top has a common factor with a number in the bottom, we can divide that number out before multipying across.

in this problem, we have 3 in the bottom of one fraction and 18 in the top of the other. we can divide 3 into 3 and get one, and we can divide 3 into 18 and get 6. so we divide the 3 out and leave these values. then we multiply across to get the new value

6. okay so i can
• divide 3 into 3 and get 1 (3 divided by 3 = 1)
• and i can divide 3 into 18, and get 6 i tryed that with my calculator and i get 0.1666666 ????
• we divide (do you mean leave out?) the 3 out and leave these values.
• Then we multiply across to get the new value......
hang on i'm working this out... Do you think you can explain it differently?

7. Originally Posted by Sazza
okay so i can
• divide 3 into 3 and get 1 (3 divided by 3 = 1)
• and i can divide 3 into 18, and get 6 i tryed that with my calculator and i get 0.1666666 ????
• we divide (do you mean leave out?) the 3 out and leave these values.
• Then we multiply across to get the new value......
hang on i'm working this out... Do you think you can explain it differently?
what you did was divide 3 by 18, it should be the other way around

look at the pic i posted. we divided 3 into 3 and the result was 1, so i replaced 3 with 1. on the top, i divided 3 into 18 as well and te result was 6, so i replace the 18 with 6. then i multiplied straight across on the top to get 12c and i multiplied straight across on the bottom to get 1 (6c = 6c/1) so the result is 12c

8. Oh okay! Thanks for explaining it again. Now i understand...

2/1 x 18 = 2/1 x 6c = 12c

Bottom: divide: 3 into 3 = 1 (replace 3 with 1)
Top: 3 divided by 18 = 6, so replace the 18 with 6!
I get it now...

Also how would i work out a question like this: A Pool is twice as long as it is wide. It is w metres wide. How many metres long is the pool?
I know you will have to find out how long the w is, but how would i do that?

9. Originally Posted by Sazza

Also how would i work out a question like this: A Pool is twice as long as it is wide. It is w metres wide. How many metres long is the pool?
I know you will have to find out how long the w is, but how would i do that?
when we say twice something, we mean two times it. "double" is another word that means 2 times. anyway, if we call the width w, then 2 times w is 2w, so that would be the length.

solution:
let w be the width of the pool
since the length is twice the width, we have:
length = 2*w = 2w meters

10. Okay so i know how to do these like a old hat, with:

1/2 x 26y
I'd divide the 2 into 2?

Like can you outline the basic steps i would take everytime i'd be asked to do this?

11. Originally Posted by Sazza
Okay so i know how to do these like a old hat, with:

1/2 x 26y
I'd divide the 2 into 2?

Like can you outline the basic steps i would take everytime i'd be asked to do this?
yes. we look for the common factors. we see a 26 in the top and a 2 in the bottom. they have a common factor of 2. so we divide 2 into 2 and get 1, so we replace the 2 with 1, and divide 2 into 26 and get 13, so we replace the 26 with 13. and take it from there

12. okay so i have this: since the 26 is a common factor of 2, you divide 2 by 2 and you get 1, so you put 1 and cross out the 2, but the 2 that has just been crossed out you divide that by 26 and you get 13, and since if you punch it into the calculator 2 divided by 26 you getta bunch of numbers so you put itL 26 divided by 2 and you get 13.
So i understand that, but how would i get the answer to the whole thingo? Would i times the 2 answers i got (13, and 1?) or what??

13. Originally Posted by Sazza
okay so i have this: since the 26 is a common factor of 2, you divide 2 by 2 and you get 1, so you put 1 and cross out the 2, but the 2 that has just been crossed out you divide that by 26 and you get 13, and since if you punch it into the calculator 2 divided by 26 you getta bunch of numbers so you put itL 26 divided by 2 and you get 13.
So i understand that, but how would i get the answer to the whole thingo? Would i times the 2 answers i got (13, and 1?) or what??
yes, we would just multiply the tops to get the tops, and multiply the bottoms to get the bottom. so the tops are 1 and 13 and y, 1*13*y = 13y, and the bottoms are 1 and 1 so 1*1 = 1, so the answer is 13y/1 = 13y

that is,

1/2 * 26y = 1/1 * 13y = 13y

14. and for the record. i noticed you had problems actually dividing stuff with your calculator, here's how to do it.

let two numbers be a and b. when we say we want to "divide b into a" or "divide a by b" or we want "a divided by b" we mean:

a/b = ?

so if i say, "what is 18 divided by 2" i mean i want to compute 18/2 = ?

now the way we do that on a calculator is that we always plug in the number we want to divide by last, that is the number at the bottom of the fraction. so we want 18 divided by 2, that means we want 18/2, since 2 is at the bottom of the fraction, we enter that number last. so on a calculator we would:

step 1: enter the number 18
step 2: press the division button
step 3: enter the number 2
step 4: press "enter" or "ans" or "=" or whatever your calculator uses to compute results