Eh, need some math expert's help here.

• mase101

  8 Nov 06, 16:06

  I'm stuck at this E maths paper 2 question, so need some help ah.
  
  Okay,
  
  The distance of two town is 600km
  
  A car travel x hours to cover the 600km which is 600 / x
  
  A plane travel 220km/h faster over same distance, which is 600 / x + 220
  
  Given that it takes 5 1/2 hours less for the plane to travel the 600km
  
  Write down an equation which x must satisfy, and show that it reduces to
  
  2x(square) - 11x - 30= 0
  
  So, it should start with this right?
  
  600 / x + 220 - 600 / x = 5 1/2
  
  Then how to continue ah? I have tried alot of method already leh. All convert to speed, buay sai. All convert to hours, also buay sai.
  
  And, did the maths clinic forum disappeared? I dont seems to find it.
  
• lageihsif

  8 Nov 06, 16:10

  Originally posted by mase101:

  I'm stuck at this E maths paper 2 question, so need some help ah.
  
  Okay,
  
  The distance of two town is 600km
  
  A car travel x hours to cover the 600km which is 600 / x
  
  A plane travel 220km/h faster over same distance, which is 600 / x + 220
  
  Given that it takes 5 1/2 hours less for the plane to travel the 600km
  
  Write down an equation which x must satisfy, and show that it reduces to
  
  2x(square) - 11x - 30= 0
  
  So, it should start with this right?
  
  600 / x + 220 - 600 / x = 5 1/2
  
  Then how to continue ah? I have tried alot of method already leh. All convert to speed, buay sai. All convert to hours, also buay sai.
  
  And, did the maths clinic forum disappeared? I dont seems to find it.
  

  
  
  dunno how to do
  friday e math paper 2....
• dark_snowboy

  8 Nov 06, 16:33

  Originally posted by mase101:

  The distance of two town is 600km
  
  A car travel x hours to cover the 600km which is 600 / x
  
  A plane travel 220km/h faster over same distance, which is 600 / x + 220
  
  Given that it takes 5 1/2 hours less for the plane to travel the 600km
  
  Write down an equation which x must satisfy, and show that it reduces to
  
  2x(square) - 11x - 30= 0
  
  So, it should start with this right?
  
  600 / x + 220 - 600 / x = 5 1/2
  
  And, did the maths clinic forum disappeared? I dont seems to find it.
  

  x- 600/(600/x + 220) =5.5
• snop_coolz

  8 Nov 06, 16:40

  pro seah...5.5*220 = 1k plus...how can only b a dis of 600km..??
• dark_snowboy

  8 Nov 06, 16:45

  Originally posted by dark_snowboy:

  x- 600/(600/x + 220) =5.5

  x- 600/(600/x + 220) =5.5
  
  5.5-x = -600/ { (600+220x)/ x }
  
  5.5-x = -600/ { (600+220x)/ x }
  
  5.5-x = -600x/(600+220x)
  
  (5.5-x) (600+220x) = -600x
  
  (5.5-x)(60+22x) = -60x
  
  330 + 121x -60x -22x(square) =-60x
  
  -22x(square) +121x + 330=0
  
  2x(square) - 11x - 30 = 0
  
• aryan

  8 Nov 06, 16:48

  i noe how, but my method could be too long coz i weak maths JC student, so hard to think simple.
  
  x=600/y where y is the speed.
  den another equation for the plane.
  x-5.5=600/(220+y) + 5.5
  den expand this equation...
  
  600/y=(600+1210+5.5y) / (220+y)
  
  end up with 600y+1210y+5.5y^2=132000+600y
  simplify and sub in the first equation y=600/x
  and den u get the ans.
  
  the main mistake u made is u misintepret the meaning of x. in here x is time, so u should look for it in terms of distance/speed.
• dark_snowboy

  8 Nov 06, 16:57

  Originally posted by aryan:

  i noe how, but my method could be too long coz i weak maths JC student, so hard to think simple.
  
  x=600/y where y is the speed.
  den another equation for the plane.
  x-5.5=600/(220+y) + 5.5
  den expand this equation...
  
  600/y=(600+1210+5.5y) / (220+y)
  
  end up with 600y+1210y+5.5y^2=132000+600y
  simplify and sub in the first equation y=600/x
  and den u get the ans.
  
  the main mistake u made is u misintepret the meaning of x. in here x is time, so u should look for it in terms of distance/speed.

  i dont remember you can do this method in Seconday school, or is it not very advisable to?
• aryan

  8 Nov 06, 17:03

  lol sry i dun rmb anything taught in sec sch for maths.
• dreamthinkdo_ers

  8 Nov 06, 17:12

  Originally posted by dark_snowboy:

  x- 600/(600/x + 220) =5.5
  
  5.5-x = -600/ { (600+220x)/ x }
  
  5.5-x = -600/ { (600+220x)/ x }
  
  5.5-x = -600x/(600+220x)
  
  (5.5-x) (600+220x) = -600x
  
  (5.5-x)(60+22x) = -60x
  
  330 + 121x -60x -22x(square) =-60x
  
  -22x(square) +121x + 330=0
  
  2x(square) - 11x - 30 = 0
  

  Correct
  (2x-15)(x+2) = 0
  x = 7.5 hr
  Spped of car =600/7.5 =80
  speed 0f plane = 300
  time for plane = 600/300 = 2hr
  difference = 7.5 - 2 = 5.5 hr
  
  There you go
• Orange*Asterisk

  8 Nov 06, 18:01

  dunno. how ah?
• Agenda

  8 Nov 06, 18:08

  walau.. this one is like free frag sia...
  
  
• tut4nkh4m3n

  8 Nov 06, 18:12

  Originally posted by Agenda:

  walau.. this one is like free frag sia...
  
  

  yeah... i learnt it in sec three. just expand all the way and then simplify it down to the simplest quad equation. lazy to do tho hehe.
• striderz_o405

  8 Nov 06, 18:23

  
  
  There you go
• ^tamago^

  8 Nov 06, 18:32

  saviour.
  
• snop_coolz

  8 Nov 06, 18:39

  can explain??
• yxTay

  9 Nov 06, 17:12

  Originally posted by mase101:
  

  The distance of two town is 600km
  
  A car travel x hours to cover the 600km which is 600 / x
  
  A plane travel 220km/h faster over same distance, which is 600 / x + 220

  As explained, the speed of the plane = ( 600 / x + 220 ) km/h
  
  Also,
  

  Originally posted by mase101:
  

  Given that it takes 5 1/2 hours less for the plane to travel the 600km

  Therefore, also, the speed of the plane = ( 600 / (x - 5.5 ) ) km/h
  
  Equating them together, (since the 2 expressions refers to the speed of the plane,)
  600 / x + 220 = 600 / (x - 5.5 )
  
  Simplify.