How do I figure out what y is in: 5 y = -55?

Question

4 y= -32; -12 y + 7 = -5; 1 - y = 5; 3 - y = -8; -1 y -8 = -9; 8y = 72; 9 y -11 = 52; -12y -1 = 83....I need help learning how to figure these out please

Answer 1

you divide the number that is to be multiplied with the variable on both sides...like your original question 5y = -55....divide 5y by 5 (that cancels out the 5) and divide -55 by 5...that gives you -11.  y = -11

Your second question4y = - 32, divide both sides by 4.

The next is -12 y + 7 = -5, deduct 7 from both sides and you get -12y = -12.  Then divide both sides by -12...you get y = 1.  Now you try some.

Answer 2

5 y = - 55

Whatever is done to one side of the "equals" sign must be done to the other.  Look at the side with the variable "y".  It is being multiplied by "5".  Since we must do the inverse in order to get "y" by itself, we divde both side by "5".

( 5 y ) / 5 = - 55 / 5

5 / 5 = 1

1 (times) y = y, so y = - 55 / 5 which is - 11.

5y=-55

y=-11

If you're adding - 12 y + 7 = - 5, then you must first subtract 7 from both sides before dividing, because the 12 is part of the y since it's being multiplied, so you can't divide both sides by 12 until you subtract 7 from both sides.  The 7 is not part of the y; it's part of 12y.  If you had -12(y+7), then you would first divide the 12, and, then subtract 7.

- 12 y + 7 = - 5

- 12 y = - 12

y = 1

- 12 ( y + 7 ) = - 5

( y + 7 ) = 5 / 12

y = - 79 / 12

Answer 3

these are simple if you know how to do them.  4y=-32.  divide both sides by 4.  that will cancel out the 4 on the left side, so you are left with y=-8.

9y-11=52. add 11 to both sides.  9y=63.  divide both sides by 9.  y=7.

etc, etc, their all the same. if you have trouble with a particular one, e-mail me, i'd be happy to help.

Answer 4

Just remember, you need to do is isolate y.  That is, have a 'y' sticking out by itself, on one side of the = sign (it doesn't matter which side).  So manipulate what you're given until you have that.

4y = -32

Here, the only thing standing between what we have (4y -- focus on just where the y occurs in what you're given, unless it's some other variable, like x) and what we want (y), is that 4.  It's multiplied, so to get from 4*y to y, we need to divide the 4*y by 4.  But, what we do to one side, we must do to the other side, always, so:

4y = -32

---   -----

4      4

y = (-32/4) = -8

Did that make sense?  Let's try another.

-12y + 7 = -5

Hmm, here we have that y multiplied by the -12 and also added to 7.  We have two choices: we can either divide both sides by -12 first, or we can subtract 7 from both sides first.  Let's try it with division first..

-12y + 7 = -5

-----------   ---

     -12       -12

y + (7/-12) = (5/12)

Now we'll get the y by itself if we move the -7/12 to the other side, so:

y + (-7/12) + (7/12) = (5/12) + (7/12)

y = (12/12) = 1

But, let's see the other way:

-12y + 7 = -5

Subtracting 7 from both sides, we have

-12y + 7 - 7 = -5 - 7

-12y = -12

And now dividing both sides by -12, we get

(-12y)/(-12) = (-12)/(-12)

y = 1.

Most people will choose to do the additions and subtractions first, in such a case, getting the y by itself on one side, with anything it's multiplied or divided by, so that they deal with fractions less.  If fractions don't bother you, do it whatever way comes to mind first.

Did that make sense?  I'll try one more.  

9y - 11 = 52

So, if we opt to get the y along with any multiples on one side first, we have to get rid of that -11, so we do the opposite (+11) on both sides:

9y - 11 + 11 = 52 + 11

9y = 63

Now we need to get rid of that pesky 9.  Since it multiplies the y we want, we do the opposite (divide by 9) on both sides:

9y = 63

---   ----

9      9

y = 7.

If you don't know your times tables, 9 is an easy one to learn.  You may know this already, but I'll type it here anyways, because Yahoo Answers are searchable, and someone else may not know.  Hold up both of your hands, with all 10 fingers spread flat.  (Forget the "is the thumb a finger?" question for a moment).  Fold down your left pinky.  Count the rest of the fingers that are up - there's 9.  1 * 9 = 9.  Now raise that up, and fold down your left ring finger.  Now you have 1 finger, then a break, then 8 fingers.  2 * 9 = 18.  Now raise that up, and fold down your left middle finger.  Now you have 2 fingers up, a break, and then 7 fingers.  3 * 9 = 27.  It works all the way up to 10 * 9!  :-)  

Anyhow, hope this helps!

Answer 5

think : 5 times what will give me -55?    if you think hard enough and work it out youll see the answer is -11 because    5(-11) = -55

Answer 6

5 y = -55

y = -55/5 or -11

U have to "undo" everything that is done to the y and get it alone on one side of the = sign.

Here's another example

y + 7 = -5... y has 7 added to it, so you need to subtract 7 from both sides

y+7-7 = -5-7

y = -12

addition "undoes" subtraction and vice versa and multiplication "undoes" division and vice versa.

You can easily do the rest now.