19. What is the probability of tossing a penny and landing on heads two times in a row?

20. The area of one playing card is 24 square centimeters. 52 cars are stacked on top of each other to make a deck. What is the volume of that solid deck?

19).

The probability of landing on heads the first time is 1/2.

The probability of landing on heads the second time is 1/2.

The probability of landing on heads both times is

(1/2) · (1/2) = 1/4 = 25%.

20).

The volume of the solid deck is

(length · width) · (height)

= (24 cm²) · (52 · the thickness of each car).