Huh Lab Maths › IGCSE Maths › Probability
Topic 8 of the Cambridge IGCSE Mathematics (0580) syllabus: from single events to combined and conditional probability. Here is what each part asks, a practice question for each, and the mistakes that cost the most marks.
Each part with one practice question, made by the same engine your child plays. Parts marked Extended are for the Extended paper only.
What is the probability of an event that is certain to happen?
1. Probabilities go from 0 (impossible) to 1 (certain).
In 80 trials, a drawing pin lands point up 28 times.
Use this to estimate how many times it happens in 160 trials.
56. Relative frequency 28/80 = 0.35. 0.35 × 160 = 56.
The probability that Ana is late is 4/6.
The probability that it rains is 2/3.
The events are independent. Find P(Ana is late AND it rains).
4/9. For independent events, AND means multiply: 4/6 × 2/3 = 4/9.
A bag holds 3 red and 4 blue counters.
Two are taken out, without replacement.
What is the probability of two reds?
1/7. First red: 3/7. One red is gone, so second red: 2/6. Multiply: 1/7.
Huh Lab checks every wrong answer against known mistakes like these, and goes back to the step behind the one your child keeps making.
Ask "out of how many?" first. "Given that..." shrinks the group you are choosing from.
After one counter is taken there is one fewer in the bag. Both numbers change.
AND means multiply (it gets less likely). OR, for events that cannot both happen, means add.
Probability is "how many I want" out of "how many ALTOGETHER".
3 choices then 4 choices make 3 × 4 = 12 outcomes: count the squares in the grid.
"One of each" can happen as red then blue OR blue then red. Add both routes.
If the ball is not put back, there is one fewer of everything on the second pick.
Re-read which colour the question asks about.
Short rounds on any topic, a new question every time, the exact mistake found, and a report to you after every session.
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