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Maths, Addmaths and Statistics: Post your doubts here!

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french410

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A body is subjected to 2 forces given by F1=10i-3j and F2=-2i+9j. Find the magnitude of the resultant force and represent it as a product of magnitude and direction?
need the answer and the working plzz
 
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french410

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Expand (1-3x) to the power 1/3, absolute value of x<1/3 in ascending powers of x up to and including the x to the power 3 term.
By substituting x=10 to power -3 in the expansion find to 9 significant figures the cube root of 997.
plzz explain
 
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RoaringInferno

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hellcat said:
STATS HELP :
Probability :

A box contains black and white cou ters. The probability of of randomly selecting a black counter is 1/6.
1.Find a) the probability of randomly selecting a white counter,
b) the smallest possible number of white counters in the box.
Emily took 2 counters out of the box and both of them were black.
2. What is the smallest possible number of white counters that could be in the box?

Emily asked each of the teachers at her school to randomly select one of the counters from the box.
3. If 25 teachers selected a white counter, estimate the number if teachers at Emily's school




Plz....do help...I need an answer urgently
Thanks in advance
Click to expand...
a) Selecting a black counter and selecting a white counter are the only possible events in this case, right? And the sum of all probabilities of an event is 1. So the Probability of getting a white counter = 1 - Probability Of Getting a Black Counter = 1 -1/6 = 5/6.
b) This is pretty simple. The question tells us that the probability of getting a white counter is 5/6. Naturally, we can only have whole numbers of white counters i.e. we can't have 0.5 white counters, 0.333 white counters or something like that. So the smallest number of white counters will be the smallest possible whole numbers which satisfy the probability ratio you have been provided with. In this case, that whole number is 5. So the smallest possible number of white counters is 5.
c) A little play of ratios here. If you use the probability of black counters you calculated in part (a), you'll be able to solve this. Make a rough table or something like this:
PROBABILITY : ACTUAL AMOUNT
1/6 : 2/x, Solve for x, and that gives you a total of 12 counters. Now if there are 12 total counters, and 2 black counters, so naturally the number of white counters becomes 12-2 =10.
d) More ratios. 25 teachers selected a white counter. Use your probability ratio here.
PROBABILITY : ACTUAL AMOUNT
5/6: 25/x, solve for x, and you get 30. Note that this is an estimated amount because some teachers may not have chosen a counter at all.
If you have a marking scheme or answer key to go with this, please let me know if I'm correct. I hope this helps you out.
 
whitecorp

whitecorp

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french410 said:
Expand (1-3x) to the power 1/3, absolute value of x<1/3 in ascending powers of x up to and including the x to the power 3 term.
By substituting x=10 to power -3 in the expansion find to 9 significant figures the cube root of 997.
plzz explain
Click to expand...

I have worked it out for you in full:



Hope this helps. Peace.
 
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zainabkhann

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i am having trouble in 3 questions for the topic: function, can someone please help me? someone with a math gce olevel past paper book (topical)
 
whitecorp

whitecorp

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zainabkhann

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whitecorp said:
You could try my collection of worked problems over here:

http://www.whitegroupmaths.com/2010/03/functions.html

http://www.whitegroupmaths.com/2012/01/functions.html

In addition, I have written a summary involving functions which you can download for free here:

http://www.a-levelmaths.com/summaryhandouts.htm (look at no. 1 under pure math summaries)

Hope this helps. Peace.
Click to expand...
do we really need to know the properties of functions in graphs? in olevels? usually the questions are quite easy and involve an equation or expression of some sort.
 
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zainabkhann

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Can someone also please, send me the gcse math revision pdf and the formula book of math pdf. I do have them but they seem to be corrupted cuz i cant open them, so if someone can again send me the two listed pdfs, then it would be great! Thanks
 
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zainabkhann

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2002 :Can someone please help me a question from past paper year : 2002 paper 1 question: 13
If someone has a past paper book then do check from there.
 
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zainabkhann

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quote="minato112, post: 383308, member: 5850"]It would have been great if U copied the question...[/quote]
Its a graph question so its better if someone can look from the past paper. It says the region R is defined by 4 inequalities. Two of these are x<less than equal to 4 and x+y>greater than equal to 5.write down the other two inequalities. Took a picture of the graph from my phone.
 

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Minato112

Minato112

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zainabkhann said:
quote="minato112, post: 383308, member: 5850"]It would have been great if U copied the question...
Click to expand...
Its a graph question so its better if someone can look from the past paper. It says the region R is defined by 4 inequalities. Two of these are x<less than equal to 4 and x+y>greater than equal to 5.write down the other two inequalities. Took a picture of the graph from my phone.[/quote]

The two other inequalities are

1) x >= 2

Find the equation of the other line

Gradient : (0 ,1 ) (4 , 5)

(5 - 1) / (4 - 0) = 1

Equation of line : (y - 1) / x = 1
: y - x = 1

Therefore the second inequality is y - x <= 1
 
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zainabkhann

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minato112 said:
Its a graph question so its better if someone can look from the past paper. It says the region R is defined by 4 inequalities. Two of these are x<less than equal to 4 and x+y>greater than equal to 5.write down the other two inequalities. Took a picture of the graph from my phone.
Click to expand...

The two other inequalities are

1) x >= 2

Find the equation of the other line

Gradient : (0 ,1 ) (4 , 5)

(5 - 1) / (4 - 0) = 1

Equation of line : (y - 1) / x = 1
: y - x = 1

Therefore the second inequality is y - x <= 1[/quote]
I know what the answer is , I want to know how to read the graph to determine the equation of line. How did you read this specific graph. I need the steps for that.
 
Minato112

Minato112

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zainabkhann said:
The two other inequalities are

1) x >= 2

Find the equation of the other line

Gradient : (0 ,1 ) (4 , 5)

(5 - 1) / (4 - 0) = 1

Equation of line : (y - 1) / x = 1
: y - x = 1

Therefore the second inequality is y - x <= 1
Click to expand...
I know what the answer is , I want to know how to read the graph to determine the equation of line. How did you read this specific graph. I need the steps for that.[/quote]
oh k

The graph he gave was x <= 4 and x + y>= 5

As for the line x < 4, its easy to identify

Now consider the line x + y = 5
Rearrange it in the form y = mx + c
It becomes : y = -x + 5

Its gradient is -ve, therefore the line will slope down.

Its y-intercept is 5, therefore we only have to identify the line which cuts the y-axis at 5 on the graph.

Hope I made it clear.
 
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zainabkhann

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Yeah you did, I knew how they got x+y=5 I was talking about how you identifed the other two ineuqlaities from the graph.
 
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