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A researcher has found old census data about Measles (M), Chickenpox (C), and Whooping cough (W) among 12-year-old children - Junior Cycle Mathematics - Question 10 - 2015

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A researcher has found old census data about Measles (M), Chickenpox (C), and Whooping cough (W) among 12-year-old children. In a group of 100 children: 31 had none... show full transcript

Worked Solution & Example Answer:A researcher has found old census data about Measles (M), Chickenpox (C), and Whooping cough (W) among 12-year-old children - Junior Cycle Mathematics - Question 10 - 2015

Step 1

Use this data to fill in the Venn diagram.

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Answer

To fill in the Venn diagram, we first identify the various subsets of children with diseases. Here's the breakdown:

  1. Children with all three diseases (M, C, W): 2
  2. Children with Measles and Chickenpox but not Whooping cough (M ∩ C ∩ W'): 2
  3. Children with Whooping cough and Chickenpox (W ∩ C): 6 (which includes those with all three, so 6 - 2 = 4 will go in W ∩ C only)
  4. Children with at least two diseases (calculated):
    • Children with Measles and Chickenpox: 2 + 2 (those with all three) = 4
    • Children with Whooping cough and Measles (W ∩ M): Not given directly, but can be deduced later.
  5. Children with only Measles: 18 - 2 (M ∩ C) - 2 (M ∩ W) = 14
  6. Children with Chickenpox only can be found as:
    • 40 (total with Chickenpox) - 2 (M ∩ C) - 4 (W ∩ C) - 2 (those with all three) = 32
  7. Children with none of the diseases: 31.

Thus filled, the counts in the Venn diagram would be:

  • Only whooping cough: 15
  • Only Chickenpox: 32
  • Only Measles: 14
  • Measles and Chickenpox only: 2
  • Whooping cough and Chickenpox only: 4
  • All three diseases: 2
  • None: 31.

Step 2

Find the probability that a child chosen at random from the group had Chickenpox.

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Answer

To find the probability that a child chosen at random had Chickenpox, we use the formula:
P(C)=Number of children with ChickenpoxTotal number of childrenP(C) = \frac{\text{Number of children with Chickenpox}}{\text{Total number of children}}
In this case, there are 40 children with Chickenpox among 100 children:
P(C)=40100=25P(C) = \frac{40}{100} = \frac{2}{5}
Thus, the probability is ( P(C) = \frac{2}{5} ).

Step 3

Complete the table.

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Answer

  1. Statement 1:
    6 had Whooping cough and Chickenpox.
    Set notation:
    6=#(WC)6 = \#(W \cap C)

  2. Statement 2:
    36 had Chickenpox but not Measles.
    Set notation:
    36=#(CM)36 = \#(C \setminus M)

  3. Statement 3:
    2 had Measles and Chickenpox but not Whooping cough.
    Set notation:
    2=#(MCW)2 = \#(M \cap C \cap W')

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