Answer:
The number of parents who volunteered to bring refreshments is 16.
Step-by-step explanation:
The information provided is:
N = 84
n (S) = 35
n (S ∩ R) = 11
n (R) = 1.5 × n (S' ∪ R')
Compute the value of n (S ∪ R) as follows:
[tex]n(S\cup R)=n(S)+n(R)-n (S\cap R)\\\\n(S\cup R)=n(S)+[1.5(N-n(S\cup R)]-n (S\cap R)\\\\n(S\cup R)=n(S)+1.5N-1.5n(S\cup R)-n (S\cap R)\\\\2.5n(S\cup R)=n(S)+1.5N-n (S\cap R)\\\\2.5n(S\cup R)=35+(1.5\times84)-11\\\\2.5n(S\cup R)=150\\\\n(S\cup R)=\frac{150}{2.5}\\\\n(S\cup R)=60[/tex]
Now compute the value of n (R) as follows:
[tex]n (R) = 1.5 \times n (S' \cup R') \\\\n (R) = 1.5 \times [N-n (S \cup R)]\\\\n (R) = 1.5 \times [84-60]\\\\n(R)=16[/tex]
Thus, the number of parents who volunteered to bring refreshments is 16.