Probability Question GCSE

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    Hi could someone explain to me how this answer is correct

    Q2 If the probability of spinning red on a spinner is 1 – 3x, find the probability of spinning any colour except red.

    answer = 3x but I don't understand how

    thanks
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    The probability of 1 includes red and every other colour.
    So if you do 1-Probability(Red), then the rest of the colours probability can be given.
    1-(1-3x) =
    1-1= 0
    You have a "-" outside the bracket and inside the bracket. Two minuses make a plus. So --3x is 3x.
    Therefore your answer is 3x
    Hope I was clear enough, please ask more questions if I wasn't clear
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    (Original post by MezmorisedPotato)
    The probability of 1 includes red and every other colour.
    So if you do 1-Probability(Red), then the rest of the colours probability can be given.
    1-(1-3x) =
    1-1= 0
    You have a "-" outside the bracket and inside the bracket. Two minuses make a plus. So --3x is 3x.
    Therefore your answer is 3x
    Hope I was clear enough, please ask more questions if I wasn't clear
    Still a bit lost if you do 1-(1-3x) and that is the same as 1-1

    so does that mean that 1-3x is equal to 1 ?
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    (Original post by samaad1)
    Still a bit lost if you do 1-(1-3x) and that is the same as 1-1

    so does that mean that 1-3x is equal to 1 ?
    Ok so it's like this. When you do 1( which is the total probability of red and all colours) - probability of red, then you get the probability of the rest. You know red has a probability of 1-3x.
    So take 1-3x from the total probability which is 1.
    1- (1-3x)
    1-1 is 0.
    Since the 1 has been sorted out, you only have the --3x left which is 3x. You got to work on the bracket in steps

    Zacken will probably explain a lot better!!
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    (Original post by MezmorisedPotato)
    Ok so it's like this. When you do 1( which is the total probability of red and all colours) - probability of red, then you get the probability of the rest. You know red has a probability of 1-3x.
    So take 1-3x from the total probability which is 1.
    1- (1-3x)
    1-1 is 0.
    Since the 1 has been sorted out, you only have the --3x left which is 3x. You got to work on the bracket in steps

    Zacken will probably explain a lot better!!
    still very confused of how can 1-3x be equal to 1
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    (Original post by samaad1)
    Hi could someone explain to me how this answer is correct

    Q2 If the probability of spinning red on a spinner is 1 – 3x, find the probability of spinning any colour except red.

    answer = 3x but I don't understand how

    thanks
    Let's say the probability of getting a red is r, then the probability of getting a blue is b, green is g, etc... do the same for every single colour. Now you know that you spinning the spinner means you must land on some colour. So the probability that you get a colour is 1. But that's the same as saying that the sum of the probabilites of getting red, green, blue, etc.. add up to 1.

    So r + b + g + \cdots  = 1. Now, for you not to get a red means that you must get a blue or green or yellow or whatvever. Which is the probability of getting one of every single colour minus the probability of getting a red.

    So since the probability of getting any colour is 1, then you subtract the probability of getting a red to get the probability of not getting a red. This is 1 - r.

    In your case, r = 1-3x so you do 1 - (1-3x) = \underbrace{1 - 1}_{=0} -- 3x = 3x. We are not saying that 1 - 3x = 1. We are saying that 1 - (1-3x) = 3x.
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    (Original post by Zacken)
    Let's say the probability of getting a red is r, then the probability of getting a blue is b, green is g, etc... do the same for every single colour. Now you know that you spinning the spinner means you must land on some colour. So the probability that you get a colour is 1. But that's the same as saying that the sum of the probabilites of getting red, green, blue, etc.. add up to 1.

    So r + b + g + \cdots  = 1. Now, for you not to get a red means that you must get a blue or green or yellow or whatvever. Which is the probability of getting one of every single colour minus the probability of getting a red.

    So since the probability of getting any colour is 1, then you subtract the probability of getting a red to get the probability of not getting a red. This is 1 - r.

    In your case, r = 1-3x so you do 1 - (1-3x) = \underbrace{1 - 1}_{=0} -- 3x = 3x. We are not saying that 1 - 3x = 1. We are saying that 1 - (1-3x) = 3x.
    thank you I think I fully understand now
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    (Original post by MezmorisedPotato)
    Zacken will probably explain a lot better!!
    (Original post by samaad1)
    thank you I think I fully understand now
    No problem, give MezmorisedPotato his fair share of credit as well
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    (Original post by Zacken)
    No problem, give MezmorisedPotato his fair share of credit as well
    yup I repped him
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    (Original post by samaad1)
    yup I repped him
    Awesome
 
 
 
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