The set A 1 2 3 4 8 X a b c d has how many elementsSolution

The set A = {1, 2, 3, 4, 8} X {a, b, c, d} has how many elements?

Solution

Answer:

Consider the set A = {1, 2, 3, 4, 8} X {a, b, c, d} then

A={(1,a),(1,b),(1,c),(1,d),(2,a),(2,b),(2,c),(2,d),(3,a),(3,b),(3,c),(3,d),(4,a),(4,b),(4,c),(4,d),(8,a),(8,b),(8,c),(8,d)}

So the number of elements of A is 5 x 4 = 20