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JAMB Mathematics 2019 Paper

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Question : 61

Total: 73

If the universal set μ = {x : 1 ≤ x ≤ 20} and

A = {y : multiple of 3}

B = |z : odd numbers}

Find A ∩ B

{1, 3, 6}
{3, 5, 9, 12}
{3, 9, 15}
{2, 3, 9}

Solution:

Concept:

Find the numbers that are both multiples of

3

and odd within the universal set.

Explanation:

The universal set is

\mu = \{1, 2, 3, \dots, 20\}

.

Set

A

contains multiples of

3

:

A = \{3, 6, 9, 12, 15, 18\}

.

Set

B

contains odd numbers:

B = \{1, 3, 5, 7, 9, 11, 13, 15, 17, 19\}

.

The intersection

A \cap B

contains elements common to both sets.

These common elements are

3

,

9

, and

15

.

Therefore,

A \cap B = \{3, 9, 15\}

.

Answer:

A \cap B = \{3, 9, 15\}

, which is option C.

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