B. The number in a Baker's dozen = 13.

C. The number of Wonders of the Ancient World = 7.

D. The number of letters in the English alphabet = 26.

E. The number of faces of an icosahedrons or the number of vertices of a dodecahedron = 20.

F. The total number of pips on a standard die = 1 + 2 + 3 + 4 + 5 + 6 = 21.

G. The number of balls used in a standard pool game — not counting the cue ball = 15.

H. The number of players in the batting order of a baseball team = 9.

I. The only cube that is one less than a square = 8. J. The cube root of this number is one more than the smallest prime = 27.

K. The number of Quidditch players on all the house teams at Hogwarts =28.
Each team had 7 players: 1 Seeker,
1 Keeper, 2 Beaters, & 3 Chasers.   There were 4 houses.

L. The maximum number of pieces into which a round pizza can be cut by making 6 cuts = 22.
The formula for the maximum number of pieces for x cuts =   .5x² + .5x + 1.

M. The only integer n for which
n = x^y = y^x, for x not equal to y is 16.
      2⁴ = 4² = 16.

N. The base of common logarithms = 10.

O. The only number whose spelling contains the same number of letters as the number itself is FOUR (4).

P. The only prime that is the sum and difference of two primes = 5.

      5 = 2 + 3 and 5 = 7 - 2.

Q. The two-digit number that is divisible by both the sum and the product of its digits = 24.
The sum of the digits = 6 and the difference of the digits = 2, & both divide into 24.

R. The smallest number of people in a room where the probability of two of them having the same birthday is at least 50 percent is 23.
      Click here for an explanation of the Birthday Problem.

S. The number feared by Pythagoreans, since it lies halfway between the only two integers that can be both the perimeter and the area of the same rectangle is 17.
The only two rectangles with area and perimeter numerically equal are the
3 x 6 rectangle and the 4 x 4 rectangle.
The perimeter and area of the 3 x 6 rectangle = 18 and the area and perimeter of the 4 x 4 rectangle = 16.

T. The number of flavors of ice cream at Baskin-Robbins minus the value of a score = 11.   31 - 20 = 11.

U. The number of months in the Julian calendar = 12.

V. The smallest perfect number = 6.
      Click here for an explanation of Perfect Numbers.

W. The number of years that you must be married to celebrate your silver wedding anniversary = 25.

X. The number of the amendment that gave women the right to vote = 19.

Y. First determine the radius of a circle when the numeric values of the circumference and the area are equal.
Then add to that number the base for the hexadecimal system.   2 + 16 = 18.
To find the radius of a circle with numerically equal area and circumference, set the formulas equal to each other:
pi * r² = 2 * pi * r     Therefore, r = 2.