# Thread: Would anyone check my solutions to a few probability questions

1. ## Would anyone check my solutions to a few probability questions

https://imgur.com/gallery/w3DX7QV

Please can you check through my solutions and see what mistakes I’m making. I must admit 17b I had no clue

2. ## Re: Would anyone check my solutions to a few probability questions

Working out for 17 a , in the HSC requires this step $( \frac{20}{20})( \frac{1}{20})$

the $( \frac{20}{20})$ ensures you get any card and the $( \frac{1}{20})$ is any other specific card

17 b is

$\binom{3}{2} \times ( \frac{1}{20})^2( \frac{19}{20}) \, = \, ( \frac{57}{8000})$

Uses binomials

3. ## Re: Would anyone check my solutions to a few probability questions

For 18

Count all the yellows and the blue only once you should get 11 total outcomes. I understand in you thinking its from the total set but if u think about it the question is talking about "atleast 3" only.

4. ## Re: Would anyone check my solutions to a few probability questions

Originally Posted by HeroWise
For 18

Count all the yellows and the blue only once you should get 11 total outcomes. I understand in you thinking its from the total set but if u think about it the question is talking about "atleast 3" only.
Are the others correct?

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