Mathematics: Post your doubts here!

[tiki-taka]

Is the markscheme ans wrong for 10 (i)
http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s15_ms_12.pdf

 

[Saad the Paki]

Is the markscheme ans wrong for 10 (i)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s15_ms_12.pdf
View attachment 59695

Ummm nope, if u use b^2-4ac you'll get (-6)^2-4 (2)(5-p) = 36-8 (5-p)<0 then solve.

 

[tiki-taka]

Ummm nope, if u use b^2-4ac you'll get (-6)^2-4 (2)(5-p) = 36-8 (5-p)<0 then solve.

Q10 i not Q11 thanks

 

[Rizwan Javed]

Q10 i not Q11 thanks

It's also correct in the ms.

 

[Rizwan Javed]

Integrate this to get the volume of revolution:

pi * y ^2 <---- y here is the equation of the curve.

 

[Saad the Paki]

Q10 i not Q11 thanks

Oops sorry

 

[usman]

Some books for A level Maths:

https://www.mediafire.com/folder/tsqgdwqtwqf44/A_Level_Maths

 

[The Sarcastic Retard]

Q3

 

[Lola_sweet]

Can someone help with i) c)
i have uploaded the tree diagram for the qs

 

[Eugene99]

Can someone help with i) c)
i have uploaded the tree diagram for the qs

At least two of the witnesses select accused person means that we can either have all three correct (cuz it says AT LEAST) or chose two correct and one wrong:
you can see from the tree diagram it can be done in four ways:
correct x correct x correct (all three correct)
wrong x correct x correct (first wrong and the next two correct)
correct x wrong x correct (second wrong and the rest correct)
correct x correct x wrong (third wrong)

multiplying the probabilities now
(1/12) x (1/12) x (1/12) = 0.00058
(11/12) x (1/12) x (1/12) = 11/1728
(1/12) x (11/12) x (1/12) = 11/1728
(1/12) x (1/12) x (11/12) = 11/1728

Now add them all together:
0.00058 +11/1728 + 11/1728 + 11/1728
= 0.0196 approx 0.02

 

[mohmed ahmed soliman]

help
how ms find the ANSWERS
only help required in parta for oct nov 2009 p61

 

[Saad the Paki]

help
how ms find the ANSWERS
only help required in parta for oct nov 2009 p61

You have four digits to fill. The first one HAS to be the number 5, otherwise you won't get a number between 5000 and 6000.
i) 3 digits left, 5 numbers to choose from. And since none can be repeated, you can choose from 5 numbers for the 2nd digit, from 4 for the 4th and from 3 for the 5th.
So the number of possibilities = 5*4*3 (aka 5P3) = 60

ii) If digits can be repeated, it means you can choose from all 6 numbers for the 3 digits left.
So, no. of possibilities: 6^3 = 216

This is awesomaholic101 's explanation so credit goes to her.

 

[Lola_sweet]

At least two of the witnesses select accused person means that we can either have all three correct (cuz it says AT LEAST) or chose two correct and one wrong:
you can see from the tree diagram it can be done in four ways:
correct x correct x correct (all three correct)
wrong x correct x correct (first wrong and the next two correct)
correct x wrong x correct (second wrong and the rest correct)
correct x correct x wrong (third wrong)

multiplying the probabilities now
(1/12) x (1/12) x (1/12) = 0.00058
(11/12) x (1/12) x (1/12) = 11/1728
(1/12) x (11/12) x (1/12) = 11/1728
(1/12) x (1/12) x (11/12) = 11/1728

Now add them all together:
0.00058 +11/1728 + 11/1728 + 11/1728
= 0.0196 approx 0.02

Thank you so much

 

[mohmed ahmed soliman]

help in part iv

 

[mohmed ahmed soliman]

help

 

[mohmed ahmed soliman]

You have four digits to fill. The first one HAS to be the number 5, otherwise you won't get a number between 5000 and 6000.
i) 3 digits left, 5 numbers to choose from. And since none can be repeated, you can choose from 5 numbers for the 2nd digit, from 4 for the 4th and from 3 for the 5th.
So the number of possibilities = 5*4*3 (aka 5P3) = 60

ii) If digits can be repeated, it means you can choose from all 6 numbers for the 3 digits left.
So, no. of possibilities: 6^3 = 216

This is awesomaholic101 's explanation so credit goes to her.

thanks but part ii is still unclear why 6 to power 3 is this a new rule

 

[DXDEVIL130]

Can anyone help me with this question?
In a spot check of the speeds x km/hr of 30 cars on a motorway, the data were summarised by Σ(x-110) = -47.2 and Σ(x-110)^2 = 5460. Calculate the mean and standard deviation of these speeds.

 

[Eugene99]

Can anyone help me with this question?
In a spot check of the speeds x km/hr of 30 cars on a motorway, the data were summarised by Σ(x-110) = -47.2 and Σ(x-110)^2 = 5460. Calculate the mean and standard deviation of these speeds.

We are given:
Σ(x-110) = -47
Σ(x-110)^2 = 5460
n=30
let y= x-110
Σy=-47.2 and Σy^2=5460

ȳ=-47.2/30 =-1.57
since y=x-1110
ȳ= x̅-110
x̅=ȳ+110
=-1.57 +110
=108.43

For SD calculate the sd of y
√Σy^2 /n -(ȳ)^2 (you know the normal formula we use to find the standard deviation, I can't seem to type it correctly)
√(5460/30)-(-1.57)^2
=13.4
SD of x =SD of y
so SD of x is 13.4 as well

 

[Rizwan Javed]

thanks but part ii is still unclear why 6 to power 3 is this a new rule

For part (ii) use the same logic as it is given in the part (i).

The first digit is fixed i.e. 5.

For the second digit, you have 6 numbers to choose from. For the third again you have 6 digits to choose from and so on.
So the no. of possibilities will become : 6*6*6 = 6^3

 

[DXDEVIL130]

We are given:
Σ(x-110) = -47
Σ(x-110)^2 = 5460
n=30
let y= x-110
Σy=-47.2 and Σy^2=5460

ȳ=-47.2/30 =-1.57
since y=x-1110
ȳ= x̅-110
x̅=ȳ+110
=-1.57 +110
=108.43

For SD calculate the sd of y
√Σy^2 /n -(ȳ)^2 (you know the normal formula we use to find the standard deviation, I can't seem to type it correctly)
√(5460/30)-(-1.57)^2
=13.4
SD of x =SD of y
so SD of x is 13.4 as well

Thanks a lot!