Question

Four different sets of objects contain 2,5,6, and 7 objects, respectively. How many unique combinations can be formed by picking one object from each set?
A 114
B 400
C 420
D 20

Answer 1

There are 2 choices for the first set, and 5 choices for the second set. Each of the 2 choices from the first set can be combined with each of the 5 choices from the second set. Therefore there are 2 times 5 combinations from the first and second sets. Continuing this reasoning, the total number of unique combinations of one object from each set is:
$2\times5\times\times6\times7=420\ combinations$