Question

If M is the set of positive multiples of 2 less than 150 and N is the set of positive multiples of 9 less than 150, how many members are there in M n N?

Answer 1

The multiples of 2 are all even numbers. So, let's just look at the multiples of 9 that are less than 150 and also even!

9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, 108, 117, 126, 135, 144

Only 8 winners today. The answer is 8 members. Fun stuff!

Answer 2

M n N: The intersection of this two set of numbers would be the numbers which are present in both sets. The easiest way of doing this would be writing the smallest set of numbers (N) and checking wich of its numbers belong to the  bigger set of numbers (M):

N: {0, 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, 108, 117, 126, 135, 144}

Now we check which of this numbers are multiples of 2 (multiples of 2 end in 0,2,4,6,8)

And those are:

M n N: {0,18,36,54,72,90,108,126,144}

This gives us a total of 9 members in M n N