4 (c) Probability (1 Viewer)

[sando]

Is it replacing or not replacing ?

 

[DeathB4Life]

i assumed it wasnt replacing for the sole reason being that its the first thing that came to my head.

"pick 3 squares" when i hear that i naturally think "3 different squares" but its open to debate.

 

[P_Dilemma]

i) What is the probability that Tanya chooses three white squares?

1/32 x 1/31 x 1/30 = 1/29760

ii) what is the probability that Tanya chooses three squares the same colour?

1/29760 x 2 = 1/14880

iii) What is the probability that the squares chosen are NOT the same colour?

1 - 1/14880 = 14879/14880

Hope they're right, or else i'm screwed...

-P_D

 

[sando]

umm sorry to tell u, but they are wrong..

half the squares are white.. not only 1 in 32.. lol

 

[helz_h]

i had...

i) What is the probability that Tanya chooses three white squares?

32/64 x 31/63 x 30/62 = 5/42

ii) not sure, but i thought it was just 5/42

iii) 1-5/42 = 37/42


I could be wrong though....

 

[helz_h]

i had...

i) What is the probability that Tanya chooses three white squares?

32/64 x 31/63 x 30/62 = 5/42

ii) not sure, but i thought it was just 10/42

iii) 1-5/42 = 37/42


I could be wrong though....

 

[DeathB4Life]

edit: guy above me correct

i think i put those answers down

*squinted face of recalling

 

[P_Dilemma]

Oh CRAP!!!!!!!

How did i screw up that bad... I must look like an idiot now...

-P_D

 

[sando]

shit.. i said replacing.. stupid question

i will lose all 5 marks now ay

 

[H.A.L.]

i had...

i) What is the probability that Tanya chooses three white squares?

32/64 x 31/63 x 30/62 = 5/42

ii) not sure, but i thought it was just 10/42

iii) 1-5/42 = 37/42


I could be wrong though....

Your pretty close.

ii.) 10/42 is correct but can be simplified to 5/21, so lets hope the marker isn't a prick and gives you the mark, as some people are fussy about these things.

iii.) P(Of three square chosen are different colour) = 1 - P(Three squares the same colour)

Therefore: 1 - 5/21 (from part ii.)

= 16/21

That's at least what I put, and I've seen a few others with the same answer.

 

[kerfuffle]

I got the same as H.A.L.

 

[fishy89sg]

do u get marks for cfpa (correct from previou answer)

 

[dunno04]

do u get marks for cfpa (correct from previou answer)

hmm...i think they do replace it.
DOn't they?

=.=

 

[meg_1_2_3_4_5]

i really really hope it was replacement... the question wasn't really that clear

 

[UzurOger]

I did this question twice...1st time not replacing so it was like 32\64 x 31\63 etc

but then i thought its a chess board so you cant loss any squares so i did it again and got an answer like 1\8 for the 1st question which seems like the logical answer meh hope i got it right

 

[izaon]

It does say she chooses three "different" squares at random
so i assume that means take out the square u just had

 

[da1]

the qn says TANYA CHOOSES THREE DIFFERENT SQUARES AT RANDOM so its without replacement

 

[ashh]

i took it that u dont replace it, but it is kinda confusing coz she could pick 1 sqaure, then replace it and pick again. spent a while thinking about it...i think it couldv been worded easier, oh well

 

[nickyroony]

I did this question twice...1st time not replacing so it was like 32\64 x 31\63 etc

but then i thought its a chess board so you cant loss any squares so i did it again and got an answer like 1\8 for the 1st question which seems like the logical answer meh hope i got it right

Yup! Likewise.

 

[acmilan]

Your pretty close.

ii.) 10/42 is correct but can be simplified to 5/21, so lets hope the marker isn't a prick and gives you the mark, as some people are fussy about these things.

iii.) P(Of three square chosen are different colour) = 1 - P(Three squares the same colour)

Therefore: 1 - 5/21 (from part ii.)

= 16/21

That's at least what I put, and I've seen a few others with the same answer.

^^correct

No replacement, otherwise you could pick the same square, which would go against picking different squares.