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## #26 2009-09-09 04:34:48

shirin
Guest

### Re: How do i work out an average?

#### Freelancer_Man wrote:

I need to work out an average for my maths homework but i tottaly forgot how and my parents are out so i cant ask them. PLEASE HEALP ME!

i need to work out the average of these numbers. 20 20 20 20 10 40 60 10 60

it's really easy,just add them together and divide by how many numbers there are.the answer is 3.33reacuring

## #27 2009-09-09 05:02:12

bobbym

Offline

### Re: How do i work out an average?

Hi shirin;

That answer is not correct, Ganesh got the correct answer in post #3

Ans = 260 / 9 = 28.88888...

Last edited by bobbym (2009-09-09 05:04:23)

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #28 2009-09-12 18:30:13

ian
Guest

### Re: How do i work out an average?

say i had 6 numbers,   5 14 22 28 34 46    lottery numbers if you will    but lets say i had around 20 random combinations..  so  6 numbers  in 20 different groups,   how would i work out the adverage 6 numbers,  i dont quite know the sum to work out the  adverage,   if i add all the numbers together  an divide by   how many  individual numbers there are ? or how many different groups of 6 ? i.e divide by 20 ?    an wouldnt this just give me 1 number?  not the adverage 6 numbers?     ive been racking my brain ALL NIGHT with this  any help  would be grreeattt!!!

## #29 2009-09-12 21:58:50

mathsyperson
Moderator

Offline

### Re: How do i work out an average?

You'd take the twenty "first numbers", add them up and divide by 20.
Then take the twenty "second numbers", and do the same.
Do that for the groups of third, fourth, fifth and sixth numbers, and you'll get your set of 6 "average lottery numbers".

If this has anything to do with the Derren Brown thing that was on yesterday, it won't help you predict the lottery numbers. It'll just give you lots of numbers in their twenties, and probably with fractional parts.

Why did the vector cross the road?
It wanted to be normal.

## #30 2009-10-30 00:33:35

notgudatmathsgrl
Guest

### Re: How do i work out an average?

william has two 10-sided spinners. the spinners are equally likely to land on eaach of thier sides. spinner A has 5 red sides, 3 blue sides and 2 green sides. Spinner B has 2 red sides, 7 blue sides and 1 green side. William spins both spiinners once. Work out the probability that spinner A & B do not land on the same colour. :dunno somebody please help me to answer this :S :|i am very confused and not.v good at maths. please helpp:down

## #31 2009-10-30 02:20:36

bobbym

Offline

### Re: How do i work out an average?

Hi notgudatmathsgrl;

It is sometimes easier to work out the probablities that something does occur rather than it doesn't.

The chance that you get 2 blues is 3 / 10 * 7 / 10 = 21 /100

The chance that you get 2 greens is 2 / 10 * 1 / 10 = 2 / 100 = 1 / 50

The chance that you get 2 reds is 5 / 10 * 2 / 10 = 10 / 100  = 1 / 10

Now just add them up and subtract from 1.

So 67 / 100 is the chance that when you spin them both once they will not land on the same color.

Last edited by bobbym (2009-10-31 05:59:47)

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #32 2009-11-25 05:00:37

Rebecca22
Guest

### Re: How do i work out an average?

I have to work this out can anyone help me

(?+?=?)

Square number ??
triangular number ??
cube number ???

as you can see there are 9 spaces I have to fit the numbers 1 to 9 in here

I know how to work out square, triangular and cubed numbers I just dont know what numbers fit in where please help!!!!

## #33 2009-11-25 12:27:48

bobbym

Offline

### Re: How do i work out an average?

Hi Rebecca22;

Is this what you are trying to do?

? + ? = ?
? + ? = ?
? + ? = ?

If you want each question mark to be a different digit from 1 to 9 then you can stop right there. There is no way to arrange 1,2,3,4,5,6,7,8,9 so that for each row the first 2 columns sum to the 3rd column.

Last edited by bobbym (2009-11-25 12:28:20)

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #34 2010-01-04 04:05:05

no-good-at-maths
Guest

### Re: How do i work out an average?

is there a difference between mean and average?

## #35 2010-01-04 23:26:07

bobbym

Offline

### Re: How do i work out an average?

Hi no-good-at-maths;

No.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #36 2010-01-22 04:47:48

Sylver
Guest

### Re: How do i work out an average?

What i don't know is, I want the average of 23.5, 23.0 and 23.3
i get........54.266666666667
but this is for an experiment. Thats not the average i need/mean to get.
is their another way?
the kind of answer i want is say...........24, for that kinda question.

## #37 2010-01-22 04:52:17

Sylver
Guest

### Re: How do i work out an average?

just had a thought...............sshould i use the mode instead of the mean???????
yeh...................i will. is this rite?

## #38 2010-01-22 04:54:49

Sylver
Guest

### Re: How do i work out an average?

just realised i meant median.
so 23.5 23.0 and 23.3 = 23.5
is this the right answer?????
ARGH!
i need serious help.

## #39 2010-01-22 05:10:33

Plucky
Guest

### Re: How do i work out an average?

Sylver............i think ur calculators wrong. or is that just me...........................?

## #40 2010-01-22 08:18:30

bobbym

Offline

### Re: How do i work out an average?

Hi Sylver;

just realised i meant median.
so 23.5 23.0 and 23.3 = 23.5
is this the right answer?????

No, that is not the median of that set of data the median is 23.3

Go here to see why:
http://www.essortment.com/all/medianmiddlest_rtiy.htm

What i don't know is, I want the average of 23.5, 23.0 and 23.3
i get........54.266666666667

Also you are not calculating the mean or average right.

(23.5+23+23.3) = 69.8 now divide by 3 , you get 23.26666

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #41 2010-01-25 01:15:34

Sylver
Guest

### Re: How do i work out an average?

er thanks but that was seriously confusing.
It turns out that my calculator was not working properly/i hadn't put it into my calculator properly. Whatever.
In the end i got what i needed so thanks for that and actually..........yeah, i see what you mean!
THANKYOU!

## #42 2010-01-25 10:51:15

bobbym

Offline

### Re: How do i work out an average?

Hi Sylver;

We are in danger of becoming a race that puts things into the computer in the beginning and takes them out at the end. With computers doing large parts of the problem for us we don't achieve the same level of comprehension. You must be involved in every part of the process. It is not a danger that is with us yet but it is certainly on the horizon, if I may say so. - Sir Michael Atiyah circa 1984

I remember discussing this point with co-workers for months as they refused to go over to computers while I got better practical answers than they did using them. I finally convinced some of them that Sir Michael's statements were idiotic. Now I am not so sure.

Nobody was and is more computer dependent than I and I can say that you shouldn't need a calculator to get the average of those 3 numbers. Most calculators have an average key and that though great, masks how the average was computed. A calculator is a black box, everyone puts things in and gets answers without knowing why or how. Please take the time to do averages of 3 numbers in your head or on paper. At least until you understand what an average is.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #43 2010-02-21 16:55:59

Janice
Guest

### Re: How do i work out an average?

#### Janice wrote:

Hey, I wonder how do you do this problem for my tutoring homework for grade 6. I know how to do simple average problems (with positive AND negative numbers), but this one I am confused. I've should've concentrated more...

Whoops, forgot to type in the problem...

Trevor bought 1500 pens for the office. One thousand of the pens cost a \$1.20 each. Three hundred of the pens cost 85 cents each and 200 pens cost only 45 cents each. What was the average cost of each pen?

## #44 2010-02-21 17:35:13

bobbym

Offline

### Re: How do i work out an average?

Hi Janice;

Do it like this:

1000 * 1.20 + 300 * .85 + 200 * .45 = 1655.45

Now divide by 1500:

1655.45 / 1500 = 1.1036333333

Average price of a pen rounding to the nearest penny is \$1.10

Do you understand this well enough to do a problem like this on your own? Or do you require more?

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #45 2010-02-22 21:08:49

Janice
Guest

### Re: How do i work out an average?

Hey, thank you so much for the help. But I'm a bit confused. What does the asterisks mean? Can you please try and explain in the 'primary school' version, as in easier. With the multiplication and division symbols? Thanks...^^

## #46 2010-02-22 21:14:29

bobbym

Offline

### Re: How do i work out an average?

Hi Janice;

I'll convert it to something more familiar to you but just so you know the asterisks mean multiplication.

Is that easier for you to understand?

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #47 2010-02-23 17:43:59

Janice
Guest

### Re: How do i work out an average?

Yes, thank you so much!! You guys are fast at replying messages on forums...

## #48 2010-02-24 02:01:44

bobbym

Offline

### Re: How do i work out an average?

Hi Janice;

Welcome to the forum. Yes, I am fast. I pride myself on my superficiality.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #49 2010-03-01 19:55:58

andipex
Guest

### Re: How do i work out an average?

#### Charlotte wrote:

gotta find the average of these numbers:

80, 78, 60

and then to find out the average of these numbers too:

29,30,20

if anyone can help would be much appreciated:D

## #50 2010-03-02 03:27:01

John E. Franklin
Star Member

Offline

### Re: How do i work out an average?

Hi andipex,
Make two go down, and one go up...
80 78 60
79 77 62
78 76 64
77 75 66
76 74 68
Make one go down 2 and one up 2...
74 74 70
Make the 74's go down by 1 and 70 up by 2...
73 73 72
72+2/3 72+2/3 72+2/3
So average is 72 + 2/3

igloo myrtilles fourmis