Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**ihtemthsbtneedtoasksmthng****Member**- Registered: 2012-12-09
- Posts: 6

yes it is! i think ive got the answer now? is it a= 160cm and b= 150cm?

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,846

No. that doesn't make sense. An average should be representative of the values in the table and so somewhere between the lowest and highest values.

Do I assume that you have been asked to work out the average for A and the average for B?

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,846

I will help you but pleae don't keep logging out or this could take ages.

What does the question actually ask you to work out?

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**ihtemthsbtneedtoasksmthng****Member**- Registered: 2012-12-09
- Posts: 6

Which of the places has more rainfall on average over the whole year?

Show working to explain your answer.

Sorry! I just had tea.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,846

Ok. think about the information. You have 12 months data altogether; 8 then 4 months for A and 10 then 2 months for B.

You need to work out how much rain fell in A altogether over the year.

For 8 months it was 10 cm every month. How much is that altogether?

Then 4 months at 20 cm every month.

Then add them together and divide by 12 for the average for A.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**ihtemthsbtneedtoasksmthng****Member**- Registered: 2012-12-09
- Posts: 6

so would A be 13.3?

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,846

Yes that's right. Notice the answer lies between 10 cm and 20 cm, but nearer to 10 because there were more months at that rainfall.

So, can you do B ?

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**ihtemthsbtneedtoasksmthng****Member**- Registered: 2012-12-09
- Posts: 6

Thank you so much! I'll try and remember that for the exam tomorrow!

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,846

hi ihtemthsbtneedtoasksmthng

Sorry, in my rush I forgot to say

Welcome to the forum.

Good luck with the exams.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**Mathegocart****Member**- Registered: 2012-04-29
- Posts: 1,862

Good Luck.

The integral of hope is reality.

Offline

**REMA****Guest**

Hello Can you please help with this:

A person wins 27 gold medals , 17 silver and 2 bronze over a period of years. (total 46 medals)

The task is to find the average placement.

It was solved by doingthis sum: 27(gold)*1 = 27 , 17(silver)* 2 = 34, 2(bronze) * 3 = 6

add 27+34+6 = 67 then divide 67 / 46 medals giving an average placement over the persons 46 races of 1.456 or

on average they came in 1.5 st place (rounded up)

What we can't get is how do you/why do you assign the values to the medals i.e Gold =1 (i-e first place) , Silver =2 (2nd place) and bronze = 3 (third place)

WE were not told that the medals carried seperate values...so we could've decided that gold = 3 (i.e highest points or even 100) and bronze = 1 (i.e lowest value, or even 0)

Can you explain why it was ok to "assume" gold = 1 etc etc...many thanks (it's my 13 yrs olds problem.)

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,846

hi REMA

Welcome to the forum.

This is called a weighted average. By applying a 'weight' to each type of medal you can take account of it being 'better' to get a higher weighted medal.

So if you wanted to 'score' countries in the Olympics, for example, your system of G = 3, S = 2 and B = 1 would make more sense.

But the purpose is to get the average placement where 1st is best and then 2nd and then 3rd. So you want the 'value' of gold to be 1.

Take an extreme example. If a player got only golds, say 20, then the calculation would be (20 x 1)/20 = 1, so the average placement would be 1, ie. the best.

If the player got 19 golds and 1 silver the calculation would be (19 x 1 + 1 x 2)/20 = 21/20 = 1.05 so the average placement has dropped a bit.

But you do need to be told the weightings.

And the system has a serious flaw. If a player gets 1 gold and 19 below bronzes the average is (1 x1 + 10 x 0)/20= 0.05 which is even better than the 20 gold player. Hhmmmm!

So you are right to be confused. So am I.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**REMA****Guest**

bob...thanks for the explanation. Clear and concise

**Ella123****Guest**

For my maths homework I need to find the average speed. I tried to add up and divide but the answer did not look right . Here are the speeds:

20 km/h and 60km/h.

I added up 20 and 60 and got 80 and then divided by 2. I them had 40km/h. As the question said that they travelled at 20 for 2 hours and 20 for only 30 minuets I do not see how 40km/h could be the answer.

Help me please!

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 108,752

Hi Ella123;

You must mean 20 km/h for 2hrs and 60km/h for 30 minutes.

2 x 20 km = 40 km

( 1 / 2) 60 km = 30 km

You travelled 70 km in 2 and 1 / 2 hrs. So you divide the 70 by ( 2 + 1 / 2 ) and get 28 km / hr. That is your average speed.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,648

An average is generally the arithmetic mean.

Offline

Average Nd arithmetic mean are the same thing.

What is your favorite color, by the way?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

I'm not crazy, my mother had me tested.

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 108,752

It seems nasty was his favorite color.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,648

You're a bit too late to ask him/her.

An average is not always the arithmetic mean - it can also be used to refer to any measure of central tendency.

Offline

Why was the post removed?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

I'm not crazy, my mother had me tested.

Offline

**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,648

Because he called us teenagers who like to show off, I think.

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 108,752

Why was the post removed?

A member reported it.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

What was the content of the report?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

I'm not crazy, my mother had me tested.

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 108,752

What the report was? That is between the member and I. He can tell you if he likes.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

Hmm, a report is not a PM. Who was the user?

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

I'm not crazy, my mother had me tested.

Offline