Quick E maths revision

• eagle

  23 Oct 08, 08:09

  This kind of question comes out 70+% of the time... Very frequent... Do make sure you know how to do :D

  

  Find
  (i) area of triangle ABD / area of triangle CBD
  (ii) area of triangle ABD / area of triangle ABC

  Something like that...

   

  For those who are not sure, the hint is below:

  

   

  To crucifixed and pillow, both of you should know how to do le hor...

• Oceane

  23 Oct 08, 08:15

  Originally posted by eagle:

  This kind of question comes out 70+% of the time... Very frequent... Do make sure you know how to do :D

  

  Find
  (i) area of triangle ABD / area of triangle CBD
  (ii) area of triangle ABD / area of triangle ABC

  Something like that...

   

  For those who are not sure, the hint is below:

  

   

  To crucifixed and pillow, both of you should know how to do le hor...

  
  Same height, so compare bases.

• eagle

  23 Oct 08, 08:25

  Originally posted by Oceane:

  
  Same height, so compare bases.

  yup, but I realise many times that there are still many pple who dun understand or dunno how to do these type of questions...

• Theguiltshow

  23 Oct 08, 10:01

  I guess the trick lies in being able to see the common height/base :-)

• eagle

  23 Oct 08, 10:03

  yup

  The question above is the simplest and most basic... Often, you will have these sort of triangles hidden within quadrilaterals and polygons, and at different angles from the above...

• crucifiedx

  23 Oct 08, 10:42

  yeah. =)

   

  for coordinate geometry, there's one formula to find length right? got some square root thing in the formula de. what's the formula ar? i forgot le.. :X

• eagle

  23 Oct 08, 10:43

  Originally posted by crucifiedx:

  yeah. =)

   

  for coordinate geometry, there's one formula to find length right? got some square root thing in the formula de. what's the formula ar? i forgot le.. :X

  square root of [(x1 - x2)^2 + (y1 - y2)^2]

  formula comes from pygathoras theorem

• crucifiedx

  23 Oct 08, 11:03

  Originally posted by eagle:

  square root of [(x1 - x2)^2 + (y1 - y2)^2]

  formula comes from pygathoras theorem

  
  thanks..

   

  then is 0.098 3 sig fig? i v blur..

• eagle

  23 Oct 08, 11:30

  Originally posted by crucifiedx:

  
  thanks..

   

  then is 0.098 3 sig fig? i v blur..

  2 sig fig, but 3 decimal point

  count from right side

   

• crucifiedx

  23 Oct 08, 11:38

  so 0.0098 is also 2 sig fig? zeros don't count?

• eagle

  23 Oct 08, 11:48

  Originally posted by crucifiedx:

  so 0.0098 is also 2 sig fig? zeros don't count?

  zeros on the left doesn't count

  so 0.000000098 is still 2 sig fig

  but 0.00908 is 3 s.f.

  0.009008 is 4 s.f.

• crucifiedx

  23 Oct 08, 11:52

  Originally posted by eagle:

  zeros on the left doesn't count

  so 0.000000098 is still 2 sig fig

  but 0.00908 is 3 s.f.

  0.009008 is 4 s.f.

  
  ok. thanks. (:

• eagle

  23 Oct 08, 11:56

  oh ya

  0.00000980 is also 3s.f.

  0.0000000098000 is 5 s.f.

  but 98000 can be 2 s.f., 3s.f., 4s.f. or 5 s.f., depending...

• crucifiedx

  23 Oct 08, 12:01

  ok.. i was looking through my tys then i realised i forgot how to do this ques:

   

  A model of a tanker is made using a scale of 1:20.

  (a) the length of the tanker is 15m. calculate the length, in cm, of the model.

   

  (b) the model holds 12 litres of liquid.

  calculate the number of litres the tanker will hold.

• crucifiedx

  23 Oct 08, 12:03

  for (a), i can get the ans but i don't understand.

  this is my working for (a):

   

  15m=1500cm

  1500/20=75cm

• eagle

  23 Oct 08, 12:07

  change all to the same unit, then you can safely multiply or divide by 20 here and there

  1:20 means 1cm : 20cm or 1 m : 20 m

   

  for part (b), it's volume. so you need to bear in mind the cube required... :D

• crucifiedx

  23 Oct 08, 12:09

  is the largest side of a triangle facing the largest or the smallest angle?

• eagle

  23 Oct 08, 12:10

  Originally posted by crucifiedx:

  is the largest side of a triangle facing the largest or the smallest angle?

  draw a triangle and see it yourself... you should be able to find the answer.

  an alternative method is to look at sine rule to prove, but you need to understand how sine functions... this one dun think you will have learned before

• crucifiedx

  23 Oct 08, 12:11

  Originally posted by eagle:

  change all to the same unit, then you can safely multiply or divide by 20 here and there

  1:20 means 1cm : 20cm or 1 m : 20 m

   

  for part (b), it's volume. so you need to bear in mind the cube required... :D

  
  ok.. but i don't undrestand part (b)..

• crucifiedx

  23 Oct 08, 12:13

  Originally posted by eagle:

  draw a triangle and see it yourself... you should be able to find the answer.

  an alternative method is to look at sine rule to prove, but you need to understand how sine functions... this one dun think you will have learned before

  ok.. is it facing the largest angle?

• eagle

  23 Oct 08, 13:04

  Originally posted by crucifiedx:

  
  ok.. but i don't undrestand part (b)..

  V litres / 12 litres = (20/1)³

   

  Originally posted by crucifiedx:

  ok.. is it facing the largest angle?

  Yup

   

• crucifiedx

  23 Oct 08, 13:35

  i understand le. thanks. (:

   

  this ques how to do ar:

   

  $5 is to be divided between alan and brenda in the ratio x:2. write down an expression, in terms of x, for alan's share.

   

  why is the ans not x/x+2?

• eagle

  23 Oct 08, 13:36

  must multiply by $5

• crucifiedx

  23 Oct 08, 13:59

  Originally posted by eagle:

  must multiply by $5

  
  why? :X

• eagle

  23 Oct 08, 14:05

  Originally posted by crucifiedx:

  
  why? :X

  x/x+2 is the fraction, the ratio, that Alan will get from the $5