16. Look at this series: 80, 10, 70, 15, 60, … What number should come next?

A. 20

B. 25

C. 30

D. 50

17. Look at this series: 2, 6, 18, 54, … What number should come next?

A. 108

B. 148

C. 162

D. 216

18. Look at this series: 5.2, 4.8, 4.4, 4, … What number should come next?

A. 3

B. 3.3

C. 3.5

D. 3.6

19. Look at this series: 8, 6, 9, 23, 87 , … What number should come next?

A. 128

B. 226

C. 324

D. 429