Number 25

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 [Calendar]  Christmas Day is on December 25.

 

[Calendar]  The number of leap years in the 20th century (01 January 1901 to 31 December 2000), following the adoption of the current Gregorian calendar, created by Pope Gregory XIII in 1582 to reform the old Julian calendar.

 

[Chemistry]  The atomic number of Manganese (Mn).

 

[Chemistry]  The composition of U.S. nickel is always of 25% nickel 75% copper, except the war-issued coins have no nickel: 56% copper, 35% silver and 9% manganese.

 

[Flag]  The number of stars along the border of the rhombus on the Arkansas state flag, representing the 25th state of the Union.

 

[Game]  In the popular TV game show “Deal or No Deal”, a contestant has the choices of one of 26 suitcases of the prizes U.S. $0.01, 1, 5, 10, 25, 50, 75, 100, 200, 300, 400, 500, 750, 1000, 5000, 10,000, 25,000, 50,000, 75,000, 100,000, 200,000, 300,000, 400,000, 500,000, 750,000 and the maximum amount is at least $1,000,000 (in a typical show).

 

[Geology]  I-25, a major U.S. North-South interstate highway, connecting Buffalo, Wyoming to Las Cruces, New Mexico, 1062 miles.

 

[Gov.]  U.S. men of age 18 through 25 must register with the Selective Service System, in case U.S. government needs rapid expansion of Armed Forces for national emergency.

 

[Gov.]  A U.S. representative must be a U.S. citizen over 25 years old and residing in the U.S. over 7 years.

 

 [History]  Arkansas became the 25th state of the U.S. on 15 June 1836.

 

[History] The 25th U.S. President: William McKinley (Republican, Ohio, 1897-1901).

 

 [History]  The number of windows on the crown of the Statue of Liberty, representing 25 gemstones found on the Earth. 

 

[History]  The first minimum wage in the U.S. was 25 cents an hour in 1938.

 

[Math.]  The number of prime numbers less than 100.

 

[Math.]  A number is divisible by 25 when it ends with 2 digits 00, 25, 50 or 75.

 

[Math.]  The first square number that is the sum of squares of 2 consecutive numbers: 25 = 52 = 32+42. Each root number in the series is 6 times the previous root number minus the earlier root number: 1, 52, 292, 1692Or in other words: 

(3, 4, 5) is the first/smallest a Pythagorean triple (lengths of 3 sides of a right triangle), where 2 sides are consecutive integers. This is the only case that 3 sides of the right triangle are 3 consecutive numbers.

 

[Math.]  One of only 3 known square numbers, which are a factorial plus 1: 25 = 52 = 4!+1, 121 = 112 = 5!+1 and 5041 = 712 = 7!+1. Mathematician Paul Erdös conjectured that these are the only such numbers, called Brown numbers.

 

[Math.]  All powers of 25 (or any number ending by 25) end with 25 (125 or 625): 252 = 625; 253 = 16,625; 254 = 390,625; 255 = 9,765,625…

Number 76 is the only other 2-digit number whose powers (of itself or any number ending by 76) end with 76. They are called automorphic numbers.

 

[Math.]  254 = 390,625 and 3+9+0+6+2+5 = 25.

 

[Math.]  (Sequence of numbers 49…950…0 and 50…050…0).

2025 = (20+25)2 = 452 and 3025 = (30+25)2 = 552 and 45+55 = 100.

 

[Math.]  The smallest 6th power that can be expressed as the sum of 6th powers: 244,140,625 = 256 =

= 16+26+36+56+66+76+86+96+106+126+136+156+166+176+186+236.

 

[Math.]  52 = 25 and if all digits are incremented (except the exponent) by 1, the equality becomes: 62 = 36.

 

[Measure]  The number of sheets of paper in a quire, (25 or 24).

 

[Medical]  The range of being overweight defined by the BMI (body mass index) is from 25 to 30. The BMI > 30 is defined to be obesity. BMI = weight (kilograms)/height2 (meters).

 

[Money]  The number of cents (pennies) in a quarter. (U.S. coins).

 

[Money]  By the U.S. law, any picture of U.S. [Money]  bill must be either 50% larger or 25% smaller than the real bill, to protect against counterfeit bills.

 

[Movie]  Name of TV show/series or movie: “25th Hour”.

 

[Sport]  The score of when a dart hitting the outer bull’s-eye in a dartboard game. The score for the bull’s-eye is 50.

 

[Tech.]  The tail numbers of the current Air Force One (Boeing 747-200B with Air Force designation VC-25A) are 28000 and 29000.

 

[Trivia]  The 25th wedding anniversary is traditionally named silver anniversary. Modernly, it may be replaced by sterling silver (or silver jubilee).

 

[Zip]  The values of the US non-denominated first-class postage stamps and later values (for the first ounce, starting 14 September 1975):

 

[Zip]  The values of the US non-denominated first-class postage stamps and later values, for the first ounce, starting 14 September 1975 at 10¢ to 44¢, in May 2009.  

Series

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A

B

C

D

E

F

G

H

 *

 *

 *

 *

 *

Value (¢)

10

13

15

18

20

22

25

29

32

33

34

37

39

41

42

44

 

[Trivia]  Popular U.S. city street speed limits: 15, 25, 30, 35, 40, 45 or 50 miles/hour.

 

25.29

[Measure]  The number of square meters (25.29285m2) in a square rod.

U.S. customary units for area measures: 1 acre = 160 square rods = 4,840 square yards = 43,560 square feet = 6,272,640 square inches = 4046.8564224 m2 & 1 square mile (1 section) = 640 acres = 2,589,988.11 m2 = 2.59 km2 = 259 hectares & 1 hectare = 2.471 acres = 10,000 m2 & 1 township = 36 square miles.

 

25.4

[Measure]  1 inch = 25.4mm (millimeters), exact definition standardized in July 1959. (U.S. customary and metric units for linear measures).

 

25.9

[Sport]  The size of an ice hockey rink: 200 feet long & 85 feet wide (or 61 meters long and 25.9 meters wide).

 

25 & 24

[History]  The 25th U.S. President: William McKinley (Republican, Ohio, 1897-1901).

His Vice Presidents were:  Garret Augustus Hobart (New Jersey, 1897-1901), the 24th U.S. Vice President and Theodore Roosevelt (New York, 1901), the 25th U.S. Vice President.