# Probability Question GCSE

Watch
Announcements
Thread starter 4 years ago
#1
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
0
reply
4 years ago
#2
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
0
reply
Thread starter 4 years ago
#3
(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 ?
0
reply
4 years ago
#4
(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!!
1
reply
Thread starter 4 years ago
#5
(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
0
reply
4 years ago
#6
(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 , then the probability of getting a blue is , green is , 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 . 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 .

In your case, so you do . We are not saying that . We are saying that .
1
reply
Thread starter 4 years ago
#7
(Original post by Zacken)
Let's say the probability of getting a red is , then the probability of getting a blue is , green is , 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 . 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 .

In your case, so you do . We are not saying that . We are saying that .
thank you I think I fully understand now
0
reply
4 years ago
#8
(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
1
reply
Thread starter 4 years ago
#9
(Original post by Zacken)
No problem, give MezmorisedPotato his fair share of credit as well
yup I repped him
0
reply
4 years ago
#10
(Original post by samaad1)
yup I repped him
Awesome
0
reply
X

Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### How would you feel if uni students needed to be double vaccinated to start in Autumn?

I'd feel reassured about my own health (20)
17.39%
I'd feel reassured my learning may be less disrupted by isolations/lockdowns (35)
30.43%
I'd feel less anxious about being around large groups (12)
10.43%
I don't mind if others are vaccinated or not (13)
11.3%
I'm concerned it may disadvantage some students (5)
4.35%
I think it's an unfair expectation (28)
24.35%
Something else (tell us in the thread) (2)
1.74%

View All
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.