# Edexcel gcse maths higher probability tree question - driving test

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#1
The question was as follows:
Someone takes a driving test in two parts, a theory and a practical
the probability of passing the theory test is 0.75
the probability of passing only one of the test is 0.36
the two events are independent.
find the probability of passing the practical test
What I did was draw a tree and label the unknowns x and y. the I set up two equations: 2x+2y=1 and 0.75x+0.25y=0.36.
then I did simultaneous equations to get an answer of 0.03
I don't know if this is right or wrong so can someone please let me know if its right or wrong and what i may have done wrong.
0
1 month ago
#2
(Original post by hamzafarrukh0)The question was as follows:
Someone takes a driving test in two parts, a theory and a practical
the probability of passing the theory test is 0.75
the probability of passing only one of the test is 0.36
the two events are independent.
find the probability of passing the practical test
What I did was draw a tree and label the unknowns x and y. the I set up two equations: 2x+2y=1 and 0.75x+0.25y=0.36.
then I did simultaneous equations to get an answer of 0.03
I don't know if this is right or wrong so can someone please let me know if its right or wrong and what i may have done wrong.

idk but i got the final answer of passing it as 0.52
what i did was i did 0.36/0.75 to get 0.48. i then took 0.48 from 1.00 to get 0.52. i dunno if this is right but my mate got the same answer as me.
0
1 month ago
#3
What are x and y? You haven't defined them at all
(Original post by hamzafarrukh0)
The question was as follows:
Someone takes a driving test in two parts, a theory and a practical
the probability of passing the theory test is 0.75
the probability of passing only one of the test is 0.36
the two events are independent.
find the probability of passing the practical test
What I did was draw a tree and label the unknowns x and y. the I set up two equations: 2x+2y=1 and 0.75x+0.25y=0.36.
then I did simultaneous equations to get an answer of 0.03
I don't know if this is right or wrong so can someone please let me know if its right or wrong and what i may have done wrong.
0
1 month ago
#4
I got 0.52 too!!!! But everyone’s saying it’s 0.72…..
0
1 month ago
#5
I saw the answer to be 0.78 but idk how they got it. I check used the answer to check backwards and everything checks out.
0.25 (1/4) X 0.78 = 0.195
1-0.78 = 0.22
0.75 (3|4) X 0.22 = 0.165
0.165 + 0.195 = 0.36
0.36==0.36
Therfore the passing probability for passing is 0.78 or 78%
0
1 month ago
#6
(Original post by hamzafarrukh0)
The question was as follows:
Someone takes a driving test in two parts, a theory and a practical
the probability of passing the theory test is 0.75
the probability of passing only one of the test is 0.36
the two events are independent.
find the probability of passing the practical test
What I did was draw a tree and label the unknowns x and y. the I set up two equations: 2x+2y=1 and 0.75x+0.25y=0.36.
then I did simultaneous equations to get an answer of 0.03
I don't know if this is right or wrong so can someone please let me know if its right or wrong and what i may have done wrong.
If the probability of passing is x, the probability of failing is (1 - x) seems to be the way most people have successfully attacked the question
Using your interesting method x + y = 1
Last edited by gdunne42; 1 month ago
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