Edexcel S2 - 27th June 2016 AM

Sorry i know this question has already been asked, but i just tried doing it myself and I'm a bit confused, its from June 2010.

Basically i worked out that:
2x+2y=20
and because your trying to find P(Y>6)
P(10-x>6) so therefore
P(X<4) = 1/2 but why isn't this the answer? why do you have to add on a 1/6 as the answer is 2/3 ??

please someone help

How do you find R in terms of X?

(Hint: it is the area of a rectangle with one length being ... and the other ...)

So it is length AP x BP = X(9-X) = 9X - X^2
a= -1, B=9?

please someone help

Correct (at least, that is what I would say too )

Okay, so I'm guessing E(R) is just the normal integral, but what are the limits, how are you supposed to work out the lower and upper limit of the area?

Use things from S1 - E(R) = E(aX^2 + bX) = E(aX^2) + E(bX) = aE(X^2) + bE(X).

Use things from S1 - E(R) = E(aX^2 + bX) = E(aX^2) + E(bX) = aE(X^2) + bE(X).

Hey I replied to you with my method on the previous page!

for part (b) why is the mode not 1?

Surely $1/4*2^2 = 1$ ?

$f(1) = (0.25) \times 1^2 = 0.25$.

A distribution X is used to model the length, in mm, of the first tear of a uPhone charger, and the PDF is specified below. However, Wapple have been careless and have lost some key details of the PDF.

$kx(1-x)$ if $0 \leq x < 0.5$

$\frac{23}{40} - \frac{3x}{20}$ if $0.5 \leq x \leq b$

0 otherwise.

a) Given that b is the minimum value greater than 0 such that f(b) = 0, find the value of b.

b) Hence find the value of k.

c) Find the expected length of the tear and the standard deviation.

d) Find the interquartile range of the length of tears.

e) Wapple send out an inspector to 5 random people who had asked for refunds. If the tear is longer than 1mm for at least 3 customers, all five will be refunded (ignoring systematic/human error). Find the probability, to 2 s.f, of Wapple giving a refund to a random group of 5 customers who have complained.

For part (b) why is the mode not 1?

Surely $1/4*2^2 = 1$ ?

I am sorry but I don't understand what you are saying I am very confused haha