BARS::Phi Road Sign on Loop 101 West in Phoenix, Arizona

This road sign is on westbound Loop 101 in Phoenix, Arizona.

The road sign says...

   +--------------------+
   | 56th St        1/4 |
   | Tatum Blvd   1 1/4 |
   | 51 South     2 1/4 |
   +--------------------+
   the numbers are:  56  (1/4)  (1 1/4)  51  (2 1/4)

   the math is:  
      sqrt(sqrt(2 1/4) - 1 1/4) + sqrt((56 - 51) * 1/4) = Phi

   observe...
      sqrt(2 1/4) = sqrt(9/4) = sqrt(9)/sqrt(4) = 3/2 = 1 1/2
      1 1/2 - 1 1/4 = 1/4
      sqrt(1/4) = sqrt(1)/sqrt(4) = 1/2
      56 - 51 = 5
      5 * 1/4 = 5/4
      sqrt(5/4) = sqrt(5)/sqrt(4) = sqrt(5)/2
      1/2 + sqrt(5)/2 = (1 + sqrt(5))/2
      Golden ratio = Phi = 1.61803399

MathBabbler took the picture used in this BARS on 7 May 2008. He had seen the road sign a few weeks earlier while driving to northwest Phoenix. On this day, MathBabbler sat in on a CSC100 class being held at Notre Dame Preparatory High School located in north Scottsdale. Upon entering the parking lot at the school, he encountered a prime-numbered 5 M.P.H. speed limit sign.


Creator: Gerald Thurman [gthurman@gmail.com]
Created: 07 May 2008

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This work is licensed under a Creative Commons Attribution 3.0 United States License.