A store sells 7 different types of envelopes and 6 different types of postage stamps. How many different combinations are there to buy an envelope and stamp?

Answer

42

Explanation

Let’s say:

Set of envelopes: {a,b,c,d,e,f,g}

Set of postage stamps: {1,2,3,4,5,6}

For an envelope you can have:

1a 2a 3a 4a 5a 6a (6 different combinations)

This applies to all 7 different types of envelopes.

Therefore 7 • 6 = 42