how many runners are left over?

Question

There were
72
runners to start a race. In the first half of the race,
1/3
of them dropped out. In the second half of the race,
2/3
of the remaining runners dropped out. How many runners finished the race?

 

Answer 1

72 - (1/3)(72) - (2/3)[72 - (1/3)(72)] = (1 - 2/3)[72 - (1/3)(72)] = (1/3)(72 - 24) = 16

 

16 runners are left.