# Math Assignment Help!

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Hi,

Is there anyone here good with computational methods (it's basically like GCSE math)?

I'm stuck on a few question and i really want to get a merit or distinction grade in this assignment so i have a good chance of getting excepted into University!

So here's the first question i need help on....

Calculate the following Binary digits:

(for this one its an addition (the minus sign is basicaly a space))
11111-
-01101
-10111

(for this one its an multiplication)
1011
1010

#### Dave

Joined Nov 17, 2003
6,970
Can I ask, is a 'space' the same idea as a 'don't care'? If not, can you explain what a 'space' is? Its ambiguity would have an impact of the accurate calculation of the result.

Can I also ask, are we dealing with signed (2's complement) or unsigned binary values here?

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Can I ask, is a 'space' the same idea as a 'don't care'? If not, can you explain what a 'space' is? Its ambiguity would have an impact of the accurate calculation of the result.

Can I also ask, are we dealing with signed (2's complement) or unsigned binary values here?

Dave
Hello Dave,

When i say space i mean there is nothing there. Because on the question paper it has a space there and when i try to put a space on this site it doesn't put a space.

The second question....no, there is no signed (2's complement) or unsigned binary values.

Thanks.

#### Dave

Joined Nov 17, 2003
6,970
Hi,

Hello Dave,

When i say space i mean there is nothing there. Because on the question paper it has a space there and when i try to put a space on this site it doesn't put a space.
So does that mean that a space is effectively a zero in the binary number? I've never come across the concept of a space in binary arithmatic (or any arithmatic for that matter). Think of decimal numbers with spaces in: 135- <= This could be any number between 1350 and 1359 and any arithmatic with this number could bring up differing results depending on what value you take.

The second question....no, there is no signed (2's complement) or unsigned binary values.

Thanks.
So if they are not signed and they are not unsigned what are they? If you haven't been told I would assume they are unsigned. Can you confirm this, since again this will have an impact on the calculated result either way.

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Hey Dave,

what i could do is scan the page for you and show you what i'm talking about, should i do that?

Because there is definitely a space there and there is no sign or anything.

If you don't understand it doesn't matter (because thats part of a distinction grade), i can move on to my next question.

#### Dave

Joined Nov 17, 2003
6,970
Hey Dave,

what i could do is scan the page for you and show you what i'm talking about, should i do that?

Because there is definitely a space there and there is no sign or anything.

If you don't understand it doesn't matter (because thats part of a distinction grade), i can move on to my next question.
Ok, scan it in and upload it as a Jpeg (not bitmap).

Thanks.

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Here is is: #### Dave

Joined Nov 17, 2003
6,970
Here is is: Ok, thanks for the scan. I am bemused as to the notation and hence can only assume that the blank spaces represent zeros. I am open to suggestion otherwise.

Therefore, assuming unsigned binary notation:

1 + 1 = 0 carry 1
1 + 1 + 1 = 1 carry 1
1 + 1 + 1 + 1 = 0 carry 0 carry 1 (Think about this one, what is '4' as binary?) - this is the bit that makes this question a distinction.

111110
001101
010111
-------

1100010 <= Note this now has an extra bit because of the carries from above.

You can verify the above by adding it as decimal: 62 + 13 + 23 = 98

Have a go, and let me know if you would like a step through (not sure how I will do it by typing, but can give it a go). You may find Volume IV - Chapter 2.5 of help.

The rules for binary multiplication are the same as for the AND gate:

0 x 0 = 0
0 x 1 = 0
1 x 0 = 0
1 x 1 = 1

The method, well just see, it will explain better than I will and I'm sure you'll get the right answer!

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Thank a lot Dave!

Let me check it (and look at the link), and i'll get back to you later today.

Thanks mate.

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Ok, thanks for the scan. I am bemused as to the notation and hence can only assume that the blank spaces represent zeros. I am open to suggestion otherwise.

Therefore, assuming unsigned binary notation:

1 + 1 = 0 carry 1
1 + 1 + 1 = 1 carry 1
1 + 1 + 1 + 1 = 0 carry 0 carry 1 (Think about this one, what is '4' as binary?) - this is the bit that makes this question a distinction.

111110
001101
010111
-------

1100010 <= Note this now has an extra bit because of the carries from above.

You can verify the above by adding it as decimal: 62 + 13 + 23 = 98

Have a go, and let me know if you would like a step through (not sure how I will do it by typing, but can give it a go). You may find Volume IV - Chapter 2.5 of help.

The rules for binary multiplication are the same as for the AND gate:

0 x 0 = 0
0 x 1 = 0
1 x 0 = 0
1 x 1 = 1

The method, well just see, it will explain better than I will and I'm sure you'll get the right answer!

Dave
Hi Dave,

I just checked it using this binary numbering system (not the link you gave me, because that was a bit to complicated for me ) and it seems your write.

Let me try and explain what i did....there is this kinda numbering system that goes from 1, 4 and etc and i checked it with this:

111110
001101
010111

...and it gave the answer you put here --> 62 + 13 + 23 and i added it, and it gave me 98, which if i go back to the binary numbering system it give me something like this 1100010 Thanks Dave, can i fire away with the next question, i've just got 6 to do #### Dave

Joined Nov 17, 2003
6,970
Ok, your tutor may ask you to show workings for the addition, at which case just follow the rules I stated in my fourth post of this thread - provided you follow the rules to the letter you will get the correct answer.

How did you go on with the multiplication problem? Is the explanation clear?

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Ok, your tutor may ask you to show workings for the addition, at which case just follow the rules I stated in my fourth post of this thread - provided you follow the rules to the letter you will get the correct answer.

How did you go on with the multiplication problem? Is the explanation clear?

Dave
Thanks mate i understand everything. Thread Starter

#### Thinker

Joined Jan 9, 2007
62
The next question i wanted to ask is this Standard Deviation. On the question they said that i have to do it in table format, Dave can your or anyone point this out to me.

#### Dave

Joined Nov 17, 2003
6,970
I'm not aware of it being called the 'table format', but what I would assume is that they expect you to work out each part of the standard deviation equation with a column. For example, you would have a table with the following columns:

x | freq | (x-x') | (x-x')^2

Where x is your data values, and freq is the number of occurances in the data set.

In the standard deviation equation:

The sum of freq = n

The mean x' = sum of x / n

The numbers can then be banged into the standard deviation equation.

Make sense?

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
If thats what they mean how am i supposed to sort out the numbers (Dice scores)?

There are 24 numbers on there, should i split them in half or what (since there is a X column and a frequency column)?

Or should all 24 numbers represent X (then what about the frequency column)?

Not sure mate.

#### Dave

Joined Nov 17, 2003
6,970
If thats what they mean how am i supposed to sort out the numbers (Dice scores)?

There are 24 numbers on there, should i split them in half or what (since there is a X column and a frequency column)?

Or should all 24 numbers represent X (then what about the frequency column)?

Not sure mate.
You can do a tally of the numbers, so for example from your dataset there are 3x15's,, 5x16's etc - this method keeps the table neat.

Otherwise, just list every number in the dataset and omit the freq column.

Just be aware that in the first method that you need to take care when working out the sum of x - if there are 3 15s then the sum of this is 45, and so on. You should probably add a column:

x | freq | xtot | (x-x') | (x-x')^2

Where xtot = x*freq

Then the mean x' = sum of xtot / n

If you understand, have a go and post up your answers.

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
I'll have a go and get back to you tomorrow is that okay?

#### Dave

Joined Nov 17, 2003
6,970
I'll have a go and get back to you tomorrow is that okay?
No problem.

Dave

Thread Starter

#### Thinker

Joined Jan 9, 2007
62
Okay Dave,

The Standard Deviation is 2.7487

Here is how i worked out the answer >CLICK<

Can you check if the way i done it is right.

#### Dave

Joined Nov 17, 2003
6,970
Okay Dave,

The Standard Deviation is 2.7487

Here is how i worked out the answer >CLICK<

Can you check if the way i done it is right.
Good job, your method is correct.

I have gone roughly through your numbers in my head and they seem correct; I would suggest that you have one more run through your basic calcs to ensure you have got the baisc multiplications and sumations right. Otherwise, well done.

Dave

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