This video is a quick reminder of probability equations for GCSE maths, and is aimed at around grade 8. The questions are fairly challenging, and you really need to read them carefully.
– stop the video
– work through the question
– compare your solution
I hope the video helps and please leave a comment – thanks!
Here’s the questions (first one on the video):
1. There are some green counters and white counters in a bag. The ratio of green counters to white counters is 4:1. Two counters are removed at random. The probability that both the counters are white is 1/30 How many counters were in the bag before any counters were removed?
2. There are 5 green counters and x white counters in a bag. Two counters are removed at random. The probability that one counter is green, and the other counter is white is 6/11 How many white counters were in the bag before any were removed?
3. There are x pens in a box. 8 of the pens are blue, and the rest are red. Ahmed takes a random pen from the box and does not replace it. He then takes another random pen from the box. The probability that Ahmed takes two red pens is 15 (a) Show that x^2 – 21x + 90 = 0 (b) Find the value of x
Download a copy of the question here:
Here’s a copy of the written answers:
These problems are fairly popular for GCSE maths, and appear on all the main examination boards such as Edexcel, AQA, OCR and Educas.
- Read the question thoroughly
- Work methodically
- Leave plenty of space for calculations 🙂
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