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There are some counters in a bag - Edexcel - GCSE Maths - Question 9 - 2020 - Paper 3

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There are some counters in a bag. The counters are blue or green or red or yellow. The table shows the probabilities that a counter taken at random from the bag ... show full transcript

Worked Solution & Example Answer:There are some counters in a bag - Edexcel - GCSE Maths - Question 9 - 2020 - Paper 3

Step 1

Start by working out the unknown probabilities

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Answer

Given the probabilities for blue and green as 0.32 and 0.20 respectively, we can denote the probability of red as P(R) and yellow as P(Y).

Since the total probability must equal 1, we can express this as:

P(B)+P(G)+P(R)+P(Y)=1P(B) + P(G) + P(R) + P(Y) = 1

Setting P(R) = 5 * P(Y), we can now substitute:

0.32+0.20+5P(Y)+P(Y)=10.32 + 0.20 + 5P(Y) + P(Y) = 1

This simplifies to:

0.52+6P(Y)=10.52 + 6P(Y) = 1
6P(Y)=0.486P(Y) = 0.48
P(Y)=0.08P(Y) = 0.08

So, P(R) = 5 * 0.08 = 0.40.

Step 2

Find the total number of yellow counters

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Answer

With a total of 300 counters, we can now calculate the number of yellow counters using the probability we found:

extNumberofYellowCounters=P(Y)×300=0.08×300=24 ext{Number of Yellow Counters} = P(Y) \times 300 = 0.08 \times 300 = 24

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