Mathematical Facts

  1. Weight of one cu. ft water = 62.425{\text{ }}lb
  2. Velocity of light in vacuum  = 2.99776 \times  {10^8}m/\sec = 186,284\,{\text{miles/sec}}
  3. Velocity of sound in dry air at 0^\circ C =  33,136\,{\text{cm}}/\sec = 1,087\,{\text{ft}}/\sec
  4. Mean radius of earth  = 3,959{\text{ }}miles = 6,371{\text{ }}km
  5. Electronic charge  = 5 \times {10^{ - 19}}{\text{ }}e.s.u
  6. Mass of electron  = - 9.1 \times {10^{ - 28}}{\text{ }}gm
  7. Polar diameter of the earth  = 7900{\text{ }}miles
  8. Equatorial diameter of the earth  = 7926{\text{ }}miles
  9. Circumference of the earth  = 25000{\text{ }}miles
  10. Total area of the earth  = 197{\text{ }}million{\text{ }}sq{\text{ }}miles
  11. Total water area  = 71\%
  12. Total land area  = 29\%

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