Set Operations Dbb459
1. **Problem Statement:**
We have three subsets of whole numbers from 1 to 20:
- $F = \{4, 6, 8, 10, 12, 14, 18\}$
- $G = \{1, 2, 3, 4, 5, 7, 9, 11, 16, 18\}$
- $H = \{1, 2, 3, 5, 7, 9, 14\}$
We need to find:
(i) $F \cap G$
(ii) $(F \cup G)^c$
(iii) $(F \cap H)^c$
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2. **Recall Set Operations:**
- Intersection ($\cap$): elements common to both sets.
- Union ($\cup$): all elements in either set.
- Complement ($^c$): elements not in the set, relative to the universal set (here, whole numbers 1 to 20).
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3. **Calculate (i) $F \cap G$:**
Find elements common to both $F$ and $G$.
$F = \{4, 6, 8, 10, 12, 14, 18\}$
$G = \{1, 2, 3, 4, 5, 7, 9, 11, 16, 18\}$
Common elements: $4$ and $18$
So, $$F \cap G = \{4, 18\}$$
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4. **Calculate (ii) $(F \cup G)^c$:**
First find $F \cup G$ (all elements in $F$ or $G$):
$F \cup G = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18\}$
Universal set $U = \{1, 2, 3, ..., 20\}$
Elements not in $F \cup G$ are:
$$U \setminus (F \cup G) = \{13, 15, 17, 19, 20\}$$
So, $$(F \cup G)^c = \{13, 15, 17, 19, 20\}$$
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5. **Calculate (iii) $(F \cap H)^c$:**
Find $F \cap H$ first:
$F = \{4, 6, 8, 10, 12, 14, 18\}$
$H = \{1, 2, 3, 5, 7, 9, 14\}$
Common element is $14$ only.
So, $$F \cap H = \{14\}$$
Complement relative to $U$:
$$(F \cap H)^c = U \setminus \{14\} = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20\}$$
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**Final answers:**
(i) $F \cap G = \{4, 18\}$
(ii) $(F \cup G)^c = \{13, 15, 17, 19, 20\}$
(iii) $(F \cap H)^c = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20\}$