Cobby's Methods Questions

[TrueTears]

Area 1 =

But the graph is an even function, i.e.

So Area 1 =

And Area 2 =

OH YEAH SH**t

[cobby]

Thanks /0,
But i don't quite follow why you multiplied the areas by 20?

[/0]

Area 1 = 10(f(-40)+f(-30)+f(-20)+f(-10)+f(0)+f(0)+f(10)+f(20)+f(30)+f(40))

But f(-40) = f(40), f(-30) = f(30), f(-20) = f(20), f(-10) = f(10)

=> Area 1 = 10(2f(40)+2f(30)+2f(20)+2f(10)+2f(0)) = 20(f(40)+f(30)+f(20)+f(10)+f(0))

I use the same reasoning for the other area.

[cobby]

Area 1 = 10(f(-40)+f(-30)+f(-20)+f(-10)+f(0)+f(0)+f(10)+f(20)+f(30)+f(40))

But f(-40) = f(40), f(-30) = f(30), f(-20) = f(20), f(-10) = f(10)

=> Area 1 = 10(2f(40)+2f(30)+2f(20)+2f(10)+2f(0)) = 20(f(40)+f(30)+f(20)+f(10)+f(0))

I use the same reasoning for the other area.

ahh kk..got it...i had to count f(0) twice ..
Thanks /0!

[cobby]

Hey,

Taken from AMC practice Questions


If then


Thanks

[Mao]

solving first equation a^2 - a - 2 = 0, solution yields a = -1, a = 2, hence a^3 = -1 or 8

[cobby]

Hey all,

A quantity of gas expands under pressure   according to the law where is the volume of gas under pressure

a) What is the average pressure as the volume changes from to ?

b) If the change in volumes in terms of is given by , what is the average pressure as the time changes from to

Thank you!

[Flaming_Arrow]

a.



i think you can do it from there

b.

v(0) = 1
v(1) = 4

[cobby]

Thanks man!

[cobby]

Hey

Can someone please take a look at my solution to this question and see if i've done anything wrong, because the answers section says i have

The average value of the function , where is?

My working out









Solutions say

Thanks guys

[cobby]

Hey all,

Rex is shooting at a target. His probability of hitting the target is 0.6. What is the minimum number of shots needed for the probability of Rex hitting the target exactly five times to be more than 25%


My working so far has been

Pr (X=5) > 0.25

nC5* (0.6)^5 * (0.4)^[n-5] > 0.25

I can't seem to get any further than this, as my calculator won't solve for 'n'

Thanks

P.S: Why isn't Latex showing up in the threads? :S

[cobby]

Hey all,

Rex is shooting at a target. His probability of hitting the target is 0.6. What is the minimum number of shots needed for the probability of Rex hitting the target exactly five times to be more than 25%


My working so far has been

Pr (X=5) > 0.25

nC5* (0.6)^5 * (0.4)^[n-5] > 0.25

I can't seem to get any further than this, as my calculator won't solve for 'n'

Thanks

P.S: Why isn't Latex showing up in the threads? :S

What calculator do you use??

Ti-89 Titanium

[cobby]

Hey all,


From a large batch of parts, a random sample of 20 parts is selected. It is found that the proportion of defective parts in this batch is 0.07. Let X denote the number of defective parts found in the sample.

a) Find
i) Pr(X=0) - Done
ii) Pr(X=1) - Done

A quality control procedure is set in place for accepting or rejecting large batches of parts.
From the random sample of 20, if the sample contains no more than 1 defective, it is accepted. If the batch contains at least 2 defectives, then it is rejected.


b) Using this process, find the probability of accepting a batch of parts. 

I need help with Part b

Thanks guys

[Flaming_Arrow]

Hey all,


From a large batch of parts, a random sample of 20 parts is selected. It is found that the proportion of defective parts in this batch is 0.07. Let X denote the number of defective parts found in the sample.

a) Find
i) Pr(X=0) - Done
ii) Pr(X=1) - Done

A quality control procedure is set in place for accepting or rejecting large batches of parts.
From the random sample of 20, if the sample contains no more than 1 defective, it is accepted. If the batch contains at least 2 defectives, then it is rejected.


b) Using this process, find the probability of accepting a batch of parts. 

I need help with Part b

Thanks guys

Pr(1>X>0)

[Mao]

Correction: