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

You are not logged in.

- Topics: Active | Unanswered

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 87,258

What happened? Where are you confused?

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

**Online**

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

so is 6 correct ? this lesson is hell of confusing

One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 87,258

Yes, I would bet my dough on it.

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

**Online**

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

i got b for #7

One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

and for 8 i got c

One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,428

hi zee-f

F has a lot of zeros. So many that (i) it's tiresome writing them all and (ii) you couldn't even enter it in a calculator like that.

So scientific notation (also known as standard index form) gives a way to show how big a number is without having to put all the zeros.

has the effect of moving the decimal point 21 places.

So start with 6.6 and move the point 21 places.

You get 6600 000 000 000 000 000 000.

That's the same number in 'ordinary' form.

Might be helpful to learn how to show the powers properly so that 1021 looks like

Bob

edit: You start with square brackets, then the word math, then close off the bracket.

Then the expression you want to show. In this case 10^{21} The curly brackets are needed when the 'power' is more than one digit.

Then finish with square bracket, /math, close square bracket.

Hint. If someone has done this sort of thing in a post, click on it, and you'll see how they made the expression. Only the opening and closing math commands will be missing.

Bob

*Last edited by bob bundy (2011-07-06 04:15:02)*

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

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 87,258

Nope! For 7 I got A.

67 000 000 = 6.7 x 10^7

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

**Online**

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

no 8 i got b my bad

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 87,258

B is correct for 8

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

**Online**

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

and for #9 i got c

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 87,258

Hi zee-f;

Bob is going help now.

Of course that result can be rigorously obtained, but who cares?

Combinatorics is Algebra and Algebra is Combinatorics.

**Online**

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,428

hi zee-f

I've put a diagram below that I use with classes when we are doing this.

You can copy it and print it off.

You want to do (9) ?

9. Divide the following numbers using scientific notation: (4 x 102)/(1 x 103)

A5 x 105

B4 x 101

C4 x 105

D4 x 10-1

E5 x 101

F5 x 10-5

Use the diagram to convert these numbers.

4 x 10^2

Write a four in the hundreds column, fill in with zeros afterwards and you get 400

Write a 1 in the thousands column, fill in with zeros and you've got 1000

So the question is asking

Opps. That's less than one so my diagram is in-complete.

I'll repost with the other half as well.

Bob

*Last edited by bob bundy (2011-07-06 04:25:10)*

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

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

so is my 9 correct ?????

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,428

no. Don't rush. Let's make sure you understand what you are doing then you'll be able to any problem like this for yourself.

Bob

part two of the diagram below.

Have a good look at both parts.

Then I'll post again.

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

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

dosnt that give me 2/5

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,544

hi zee-f

yes that is correct,but try to get a power of ten in the numerator.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

do 4*10^-1= 2/5

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,544

hi zee-f

that is correct.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

so*

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

thanx alot

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,428

hi zee-f

The two diagrams OVERLAP at units. If you print them both and cut then them out you'll have two strips; the large numbers are on the left. This strip goes from units, through tens, hundreds all the way up to thousand millions. I had to stop there because I wanted something I could print for my students that would fit on a page.

The second strip starts at units and goes smaller as you go rightwards, down to the fraction 1 over a thousand million (0.000000001). The '1' is in the thousand millionth column.

You can join the strips to make one long strip by overlapping the units column and sticking them together. At the join the columns should go ......... hundreds, tens, units (ONCE!), then tenths, hundredths .........

Does this make sense so far?

edit: While I was typing that I see you've jumped ahead and got the answer. Well done. But you didn't need to go via 2/5.

Go back to 400/1000 = 4/10.

Look at diagram two. Put a '4' in the tenths column and you can see the right power is 10 to the -1. So you get to

So using the diagrams you can get straight to the right answer.

Bob

*Last edited by bob bundy (2011-07-06 04:43:32)*

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

yup thanx for the help

oooh and for #10 i got d

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,544

hi zee-f

that is incorrect.how did you get that answer?

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,428

Oh hang on. I was just checking that. I think d is correct.

But it isn't helping us to help you when you aren't showing the powers properly. It makes it hard to sort out the questions and the possible answers.

Bob

Offline

**zee-f****Member**- Registered: 2011-05-12
- Posts: 1,220

Perform the following calculation: (1 x 10^2)(2 x 10^3)/(1 x 10^2)

because 1*100=100

2*1000=2000

200000\(1*10^2)

200000\100=2000

Offline