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WAEC Mathematics 2012 Paper

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Question : 24

Total: 49

If p = {prime factors of 210} and Q = {prime less than 10}, find p

\cap

Q

{1,2, 3}
{2, 3, 5}
{1, 3, 5,7}
{2,3,5,7}

Solution:

Concept:

Find the intersection of the set of prime factors of

210

and the set of prime numbers less than

10

.

Explanation:

Prime factors are prime numbers that divide

210

exactly.

210 = 2 \times 3 \times 5 \times 7

So,

P = \{2, 3, 5, 7\}

.

Prime numbers less than

10

are

2, 3, 5, 7

.

So,

Q = \{2, 3, 5, 7\}

.

Therefore,

P \cap Q = \{2, 3, 5, 7\}

.

Answer:

D.

\{2, 3, 5, 7\}

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