Question

If C = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} and D = {numbers divisible by 3 from 1 to 21}, what is C ∩ D?

Answer 1

D = {numbers divisible by 3 from 1 to 21}

D = {3,6,9,12,18,21}

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C ∩ D = set of everything that is in BOTH sets C and D

C ∩ D = {3,6,9}

Answer 2

Notice how the elements 3, 6 and 9 are in BOTH sets C and D, so this is why C ∩ D = {3,6,9}