Pearson Edexcel International GCSE in Mathematics (Specification A) · 4MA1 · Free · no account needed
Conditional Probability — exam questions
10 original Incandio exam-style questions on Conditional Probability, 26 marks, about 31 minutes of writing. Each one carries the command word, the tariff and the specification statement it assesses, exactly as a paper presents them. This is an original Incandio practice question, written to reflect the structure and demands of the qualification. It is not an official Pearson Edexcel past-paper question.
This is the practice set for Conditional Probability — the module that teaches it. Read the module first if the idea is new; come here when you want to find out whether you can turn it into marks. Completely free, no account needed to read.
What these questions ask of you
6 command words run through this set, and on Pearson Edexcel International GCSE Mathematics A each one means something precise. Answering the wrong command is the commonest way a candidate who understands the module still loses the mark.
- Write down (1–2 marks)
- a value that needs no working — read off, recalled or stated
- Work out (1–5 marks)
- a calculated result, with the working that produced it
- Calculate (1–5 marks)
- a numerical answer obtained by calculation
- Explain why (1–2 marks)
- one short justification — mathematics almost never asks for extended explanation
- Find (1–5 marks)
- a value or expression obtained by a method the learner chooses
- Show that (2–5 marks)
- every step of a derivation to a value that is already printed in the question Misread as: stating the printed answer again instead of deriving it
Assessed on Paper 1 and Paper 2.
Where these sit in the specification
Pearson Edexcel International GCSE Mathematics A (4MA1) — statement 6.3. Incandio is aligned to this specification; it is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording.
The 10 questions
Answer them on paper, then open the module's exam practice to have them marked. The mark scheme, the accepted and rejected answers and the annotated model answer are in Incandio and are not printed here — an answer beside its question is not practice.
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(1)Write down
One of the 120 students is chosen at random. Write down the probability that the student plays a sport.
120 students, by year group and by whether they play a school sport Plays a sport Does not play Total Year 10 34 26 60 Year 11 26 34 60 Total 60 60 120 (Total for Question 1 = 1 mark)
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(2)Work out
A student is chosen at random from Year 10. Work out the probability that the student plays a sport.
120 students, by year group and by whether they play a school sport Plays a sport Does not play Total Year 10 34 26 60 Year 11 26 34 60 Total 60 60 120 (Total for Question 2 = 2 marks)
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(2)Calculate
A student who plays a sport is chosen at random. Calculate the probability that the student is in Year 11.
120 students, by year group and by whether they play a school sport Plays a sport Does not play Total Year 10 34 26 60 Year 11 26 34 60 Total 60 60 120 (Total for Question 3 = 2 marks)
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(1)Explain why
Nearly everyone who has flu has a headache, but few people with a headache have flu. Explain why these two statements are not in conflict.
(Total for Question 4 = 1 mark)
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(2)Find
A drawer holds 7 black socks and 5 grey socks. Two socks are taken at random without replacement, and the first one is black. Find the probability that the second is also black.
(Total for Question 5 = 2 marks)
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(3)Show that
In a club of 50 members, 30 play chess, 20 play bridge and 8 play both. A member who plays chess is chosen at random. Show that the probability the member also plays bridge is 4/15.
(Total for Question 6 = 3 marks)
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(3)Work out
A factory has two machines. Machine A makes 60 per cent of the parts and 2 per cent of them are faulty; machine B makes the rest and 5 per cent of those are faulty. Work out the probability that a randomly chosen part is faulty.
(Total for Question 7 = 3 marks)
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(4)Find
In a large population, 3 per cent have a certain condition. A screening test is positive for 90 per cent of those who have it and for 8 per cent of those who do not. One person tests positive. Find the probability that this person has the condition, to 3 significant figures.
(Total for Question 8 = 4 marks)
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(3)Calculate
Of 40 people surveyed, 24 own a car, 18 own a bicycle and 6 own neither. Calculate the probability that a person who owns a bicycle also owns a car.
(Total for Question 9 = 3 marks)
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(5)Work out
A box contains 7 white and 5 black counters. Two counters are taken at random without replacement. Work out the probability that the two counters are different colours.
probability = ............................
(Total for Question 10 = 5 marks)
Have them marked, then defend the answer
Practice tells you the mark; teaching it back tells you whether you understand it. On Incandio a topic counts as mastered only once you have taught it and defended it.
- Mark these questions — 10 questions, marked on Incandio against the authored scheme, with the mistake you actually made named.
- Teach it — explain Conditional Probability to Ember, an AI pupil who does not have it yet and asks the awkward question.
- Defend it — argue it against Thomas Bayes over three rounds, marked against descriptors you can read first.
Completely free. No subscriptions, no paywalls, no account needed to start.
Back to the module
- Conditional Probability — Probability when you already know something — shrinking worlds, 'given that' questions, and combining branches over changing conditions. Higher Tier.
- All of Incandio Mathematics · Incandio Exam Practice