Question 1
Count the total number of rectangles (including squares) in the 2x3 grid below:
+---+---+---+
| | | |
+---+---+---+
| | | |
+---+---+---+
Number of ways to choose 2 horizontal lines = C(3,2) = 3, Number of ways to choose 2 vertical lines = C(4,2) = 6. Total = 3 × 6 = 18