help with simple binomial prob Q (1 Viewer)

[mreditor16]

usually a topic I'm fine with.

but struggling with this q and getting the desired answer of 0.0124 for question a)

here it is:

 

[Carrotsticks]

Show us your working out so we can tell you what's wrong with it.

 

[mreditor16]

first of all, not getting the provided answer.

anyway, here's my working:

probability = (12/30)^2 x (18/30)^3

isn't it that simple, because order is given/set. - i.e. first two days are clear, last 3 wet...


lol mindblanking...

 

[mreditor16]

lol Carret?

 

[Carrotsticks]

You should have multiplied those results. This is because we are having the first two days being done AND the next three days being wet.

Regardless I got 0.03456.

 

[mreditor16]

You should have multiplied those results. This is because we are having the first two days being done AND the next three days being wet.

Regardless I got 0.03456.

soz that was a typo.

and yes I got the same, but Cambridge says 0.0124. this is from 10J, year 12 3u Cambridge.....

 

[mreditor16]

for b), could you confirm answer is 0.68256.


answers say 0.7102


wow Cambridge is rarely wrong...

 

[Carrotsticks]

I get the same result. Unless I'm missing something, I cannot see anything wrong with that answer.

 

[mreditor16]

ok thanks carret. silly Cambridge lol.

 

[Carrotsticks]

ok thanks carret. silly Cambridge lol.

Let's not assume just yet.

It could very well be the case that something has been missed.

 

[mreditor16]

Let's not assume just yet.

It could very well be the case that something has been missed.

e.g. .........

 

[photastic]

Got the same answers as carrotsticks. Therefore carrotsticks > cambridge