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Maths question

Helen is taking part in a quiz on TV.
The probability she answers a question correct is 4/5.
Helen is asked 3 questions
Calculate the probability she answers all three questions correctly


hELP!
Original post by lala5646
Helen is taking part in a quiz on TV.
The probability she answers a question correct is 4/5.
Helen is asked 3 questions
Calculate the probability she answers all three questions correctly


hELP!

The probability is 4/5 times 4/5 times 4/5
Reply 2
Avatar for lala5646
lala5646
OP
8
Original post by harrysbar
The probability is 4/5 times 4/5 times 4/5

but why did u do that
Original post by lala5646
but why did u do that

Because the probability the first time was 4/5 and then the probability the second time was 4/5 and then the probabilty the third time was 4/5.

The probability of it happening all 3 times in a row is quite low.
Original post by harrysbar
Because the probability the first time was 4/5 and then the probability the second time was 4/5 and then the probabilty the third time was 4/5.

The probability of it happening all 3 times in a row is quite low.

What answer did you get by multiplying the 3 events?
Reply 5
Avatar for lala5646
lala5646
OP
8
i got 64/125
prob tree.png
With each question she answers there a 0.8 chance that she will get it right, and a 0.2 chance that she will get it wrong.
The total probability of any outcome is the individual probabilities multiplied by each other.
So, if she answered correct, correct, wrong, the probability would be 0.8*0.8*0.2.
I have visualised this in a tree diagram which shows all of the possible outcomes.
It is also worth noting with tree diagrams, the total probabilities of all the branches add up to 1. (All 8 total probabilities add up to 1)
Reply 7
Avatar for lala5646
lala5646
OP
8
so was i correct/

Original post by OJlongley
prob tree.png
With each question she answers there a 0.8 chance that she will get it right, and a 0.2 chance that she will get it wrong.
The total probability of any outcome is the individual probabilities multiplied by each other.
So, if she answered correct, correct, wrong, the probability would be 0.8*0.8*0.2.
I have visualised this in a tree diagram which shows all of the possible outcomes.
It is also worth noting with tree diagrams, the total probabilities of all the branches add up to 1. (All 8 total probabilities add up to 1)
Original post by lala5646
i got 64/125

Yes that’s right :smile:

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