Find the number that fits somewhere into the middle of the series. Some of the items involve both numbers and letters
11.  Look at this series: J14, L16, __, P20, R22, ... What number should fill the blank?
A. S24
B. N18
C. M18
D. T24

12.  Look at this series: 4, 7, 25, 10, __, 20, 16, 19, ... What number should fill the blank?
A. 13
B. 15
C. 20
D. 28

13.  Look at this series: XXIV, XX, __, XII, VIII, ... What number should fill the blank?
A. XXII
B. XIII
C. XVI
D. IV

14.  Look at this series: 0.15, 0.3, ____, 1.2, 2.4, ... What number should fill the blank?
A. 4.8
B. 0.006
C. 0.6
D. 0.9

15.  Look at this series: U32, V29, __, X23, Y20, ... What number should fill the blank?
A. W26
B. W17
C. Z17
D. Z26