Maths !

• bonkysleuth

  23 Jan 08, 18:12

  Light travels at a speed of 300 000 000m/s.
  
  taking the distance from the sun to the pluto to be 5.91 X 10^9 km, find the number of seconds that light takes to travel this distance.
  
  The next question is...
  
  7y^2/3 DIVIDE 14y^ -1/2
  
  My answer's 1/2 y^7/6. But the answer on the book comes out as 1/2 y^ 5/6.
• dbowie

  23 Jan 08, 18:29

  19.7 second for the first one ? I might be wrong as I am using the computer's calculator.
  5.91 x 10^9 / Speed of Light = Time in seconds
  Thus ,
  5.91 x 10^9 / 3 x 10^8 = 19.7
  
  For the second question I got .5y^7/6 too.
• bonkysleuth

  23 Jan 08, 18:37

  Originally posted by dbowie:

  19.7 second for the first one ? I might be wrong as I am using the computer's calculator.
  5.91 x 10^9 / Speed of Light = Time in seconds
  Thus ,
  5.91 x 10^9 / 3 x 10^8 = 19.7
  
  For the second question I got .5y^7/6 too.

  Thanks. But dont you have to convert the unit to either km or metres first before being able to find the time in secs?
• wishboy

  23 Jan 08, 20:26

  Originally posted by bonkysleuth:

  Light travels at a speed of 300 000 000m/s.
  
  taking the distance from the sun to the pluto to be 5.91 X 10^9 km, find the number of seconds that light takes to travel this distance.
  
  The next question is...
  
  7y^2/3 DIVIDE 14y^ -1/2
  
  My answer's 1/2 y^7/6. But the answer on the book comes out as 1/2 y^ 5/6.

  5.91*10^9 km = 5 910 000 000 000 m
  Distance = Speed*Time
  Time = Distance/Speed
  . = 5 910 000 000 000/300 000 000
  . = 19700 s
  
  [7y^(2/3)] / [14y^(-1/2)]
  = [y^(4/6)] / [2y^(-3/6)]
  = (1/2)[y^(4/6 + 3/6)]
  = (1/2)y^(7/6)
  
  either ur book answer wrong or u copy the qn wrongly