Desperate help needed!? PLEASE :D (1 Viewer)

[bec_peace]

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there are 15 balls in a box and 4 are defective. 3 are chosen randomly from the box
whats the probabity:
1) FIRST Ball is defective?
2) all 3 are defective
3)exactly 1 of the 3 balls are defective?

Can use tree diagram...
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[Sadiah]

...am....allergic...to..maths..

 

[bec_peace]

...am....allergic...to..maths..

Oh wow that Really helped. thanks :mad1:

 

[hscishard]

Oh wow that Really helped. thanks :mad1:

a) is definitely 4/15

b)pretty sure its 4/15 x 3/14 x 2/13 (tree diagram)[No I'm not going to draw one]

c) Not very sure, haven't drew a diagram sorry.

 

[hscishard]

c) it might be (4/15 x 11/14 x 10/13) + (11/15 x 4/14 x 10/13) + (11/15 x 10/14 x 4/13)

I really hate data and probability.

 

[frenzal_dude]

c) it might be (4/15 x 11/14 x 10/13) + (11/15 x 4/14 x 10/13) + (11/15 x 10/14 x 4/13)

I really hate data and probability.

Yeh you're right:

a) 4/15
b) 4/455
c) 44/91

You really need to draw a tree diagram to work this out.