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GCSE Mathematics Problem Solving Data Higher Tier.
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GCSE Mathematics Problem Solving Data Higher Tier
There are 12 boys in Miss Jones’ Mathematics class. 5 have brown eyes, 4 have green eyes and 3 have blue eyes. She randomly chooses three different boys to answer her questions. What is the probability that at least one of the boys chosen will have green eyes? • What does the question ask us to find? • P(at least one green eyed boy) = ? • What information is given in the question? • Brown eyes – 5 • 12 • Green eyes – 4 • 12 • Blue eyes – 3 • 12
Consider the possible outcomes • GBrBl or GBrBr or GBlBl or GBlBr or • GGBl or GGBr or GBlG or ... • Is there a quicker or easier way? • P(at least one green) + P(no green) = 1 • P(at least one green) = 1 – P(no green) • P(no green) = ? • Consider how many pupils do not have green eyes • Brown eyes + Blue eyes = 5 + 3 • 12 12 • = 8 • 12
8 • 12 • 7 • 11 • 6 • 10 • x • x • P(no green) = • = 2 x 7 x 3 • 3 11 5 • = 42 • 165 • = 14 • 55 • What did the question ask us to find? • P(at least one green) = 1 – P(no green) • = 1 - 14 • 55 • = 41 • 55