Then I need to ask if you are not including the cover thickness in the 2.5" size, if not then the answer is 29.5", according to my reckoning.
Did a little update on the other questions;
CLASSIC LIST
Question Answers
1 1 = W on a U 1 wheel on a unicycle
2 3 = B M (S H T R) 3 Blind Mice (See How They Run)
3 3 = W on T 3 wheels on a tricycle
4 4 = Q in a G 4 quarts in a gallon
5 5 = D in a Z C
6 5 = T on a F 5 toes on a foot
7 6 = O in an I 6 outs in an inning
8 7 = D in a W 7 days in a week
9 7 = W of the A W 7 wonders of the ancient world
10 8 = S on a S S 8 sides on a stop sign
11 8 = T on a O 8 tentacles on a octopus
12 9 = L of a C 9 lives of a cat
13 9 = P in the S S 9 planets in the solar system
14 9 = S F in a S Y 9 square feet in a square yard
15 11 = P in a F (s) T 11 players in a football team
16 12 = D of C 12 days of Christmas
17 12 = I in a F 12 inches in a foot
18 12 = M in a Y 12 months in a year
19 12 = S of the Z 12 signs of the Zodiac
20 13 = L in a B D 13 loaves in a bakers dozen
21 13 = S on the A F 13 stripes on the American flag
22 15 = P in a R T
23 18 = H on a G C 18 holes on a golf course
24 23 = P of C in the H B
25 24 = H in a D 24 hours in a day
26 26 = L of the A 26 letters of the alphabet
27 27 = B in the N T 27 books in the New Testement
28 29 = D in F in a L Y 29 days in February in a leap year
29 32 = D F at which W F 32 degrees Fahrenheit at which water freezes
30 39 = B of the O T 39 books of the Old Testament
31 40 = D and N of the G F 40 days and nights of the great flood
32 52 = W in a Y 52 weeks in a year
33 54 = C in a D with the J 54 cards in a deck with the jokers
34 60 = M in a H 60 minutes in a hour
35 64 = S on a C B 64 squares on a chess (checker) board
36 66 = B of the B
37 88 = P K 88 piano keys
38 90 = D in a R A 90 degrees in a right angle
39 200 = D for P G in M
40 365 = D in a Y 365 days in a year
41 1000 = Y in a M 1000 years in a millennium
42 1001 = A N 1001 Arabian Nights
