A primary maths question I can't solve...

• newcomer

  5 Apr 06, 23:43

  Originally posted by stem_-_daimyou_asobi_hen:

  let mr koh salary be "x".
  his wife salary would be "3/4 x"
  
  $$ Mr koh spend is : x - 246
  $$ his wife save is : 3/4x - 246
  
  "If Mr Koh's expenditure to that of his wife is in the ratio 18:13"
  hence,
  13 ( x -246 ) = 18 ( 3/4x - 246 )
  13x - 3198 = 13.5x - 4428
  0.5x = 1230
  x = 2460
  
  their combined salary is : x + 3/4x
  =7/4 x
  =7/4 ( 2460 )
  =$4305 !
  
  hope i'm right... well .. if it's a primary school question & there's no algebra.. guess u have to use table instead. (sorrie can't realli draw here.)

  God has spoken.
• Ecxentrique

  5 Apr 06, 23:43

  Originally posted by stem_-_daimyou_asobi_hen:

  let mr koh salary be "x".
  his wife salary would be "3/4 x"
  
  $$ Mr koh spend is : x - 246
  $$ his wife save is : 3/4x - 246
  
  "If Mr Koh's expenditure to that of his wife is in the ratio 18:13"
  hence,
  13 ( x -246 ) = 18 ( 3/4x - 246 )
  13x - 3198 = 13.5x - 4428
  0.5x = 1230
  x = 2460
  
  their combined salary is : x + 3/4x
  =7/4 x
  =7/4 ( 2460 )
  =$4305 !
  
  hope i'm right... well .. if it's a primary school question & there's no algebra.. guess u have to use table instead. (sorrie can't realli draw here.)

  the algebraic method would be more straightforawrd and obvious.. and now this method and the non-algebra mtd has gotten the same answer.. so should be right lah..
• Ecxentrique

  5 Apr 06, 23:44

  Originally posted by newcomer:

  God has spoken.

  so u were after the algebraic mtd all along??
• DeathEdge

  5 Apr 06, 23:46

  kau.. and i was trying to simplify it to primary sch level maths.. =/
• Ecxentrique

  5 Apr 06, 23:47

  Originally posted by DeathEdge:

  kau.. and i was trying to simplify it to primary sch level maths.. =/

  haha but a good brain workout before the end of the night..
• newcomer

  5 Apr 06, 23:48

  Originally posted by Ecxentrique:

  so u were after the algebraic mtd all along??

  Haha, I wasn't satisfied with the simpler method(which I think is more beautiful and genius) simply because it was too simple that I missed it and it kind of hurt my ego, so to speak, lol.
  The algebra method works too but it's complicated.
• stem_-_daimyou_asobi_hen

  5 Apr 06, 23:48

  opps .. there has been a typo ..
  
  $$ Mr koh spend is : x - 246
  $$ his wife spend is : 3/4x - 246
• stem_-_daimyou_asobi_hen

  5 Apr 06, 23:51

  Originally posted by newcomer:

  Haha, I wasn't satisfied with the simpler method(which I think is more beautiful and genius) simply because it was too simple that I missed it and it kind of hurt my ego, so to speak, lol.
  The algebra method works too but it's complicated.

  Yeah, i totally agree with u. the simpler method is more striaghtforward and sweet. But i reckon the pri school teacher would want a more concrete proof of their answer, so guess "draw the table" is a better answer as well as a teaching material.
• newcomer

  5 Apr 06, 23:53

  Originally posted by stem_-_daimyou_asobi_hen:

  Yeah, i totally agree with u. the simpler method is more striaghtforward and sweet. But i reckon the pri school teacher would want a more concrete proof of their answer, so guess "draw the table" is a better answer as well as a teaching material.

  Yes, concrete is the word.
• Ecxentrique

  5 Apr 06, 23:56

  back then we weent allowed to use algebra.. haha kids are missing all the fun these days.. all the drawings of bar graphs..
  
  but for some.. it can be a hell to conceptualise and put all the numbers into the proper proportion graphically..
• Li Ka Shing

  6 Apr 06, 00:18

  What table are you guys talking about? I have no recollection of any tables. What does it look like?
• hegu

  6 Apr 06, 00:20

  wah...pri sch maths getting more and more difficult liao!
  
  anyway the table means models/diagram/bars usually drawn in problem sums
• SGpork

  6 Apr 06, 00:24

  wtf
  
  primary sch maths?
  
  
  
  
• digicharat

  6 Apr 06, 00:28

  wtf is this?
• digicharat

  6 Apr 06, 00:30

  shouldnt primary school math be like this?
  100+1=101
  100-1=99
  100*2=200
  100/2=50
  
  
• borntolive

  6 Apr 06, 00:31

  Originally posted by digicharat:

  shouldnt primary school math be like this?
  100+1=101
  100-1=99
  100*2=200
  100/2=50
  
  

  u wish..i think pri 1 will know how to do all this by now
• stem_-_daimyou_asobi_hen

  6 Apr 06, 00:42

  Originally posted by borntolive:

  u wish..i think pri 1 will know how to do all this by now

  yeah, nowsday i see primary school maths getting more diffcult like my sec hw.
  think it's really stressful for them. imagine by the time i have my own children, tink they will be doing integation by pri6.
• digicharat

  6 Apr 06, 00:43

  Originally posted by borntolive:

  u wish..i think pri 1 will know how to do all this by now

  what?!
  unbelievable!!!
• Master -_-

  6 Apr 06, 00:45

  Possible Scenario
  
  The Mummy: Boy, how was your 1st maths lesson? Ok or not?
  Pri 1 School Kid: Ok Mummy..We learnt Trigonometry,Integration, Differention and Logarithms.
  The Mummy: Wtf
• newmanmback

  6 Apr 06, 12:07

  Let mr koh salary be X
  let Mr koh expenditure be Y
  both koh and wife save 246 each
  thus koh wife salary is 0.75x
  thus koh wife expennditure is 0.72y
  
  all workings and sub-answers and answers rounded into 2 decimal places
  
  x-y= 246 --------------- (1)
  0.75x-0.72y= 246 --------------- (2)
  
  from (1): y=x-246-------------(3)
  
  substitute (3) into (2)
  From (2): 0.75x - 0.72(x-246) = 246
  0.75x - 0.72 + 177.12 = 246
  0.03x = 68.88
  x = 2296 --------- (4)(mr koh salary)
  
  substitute (40 into (1)
  from (1): x - y =246
  2296 - y = 246
  y = 2050 (mr koh expenditure)
  
  koh wife's salary = 0.74 x 2296 = 1722
  koh wife's expenditure = 0.72 x 2050 = 1476
  
  so the SALARIES of the couple are 2296(mr koh) and 1722(koh's wife)
  their total salary is 4018
  
  as for the proofing...some exam wuestions want u to prove the 3/4 and 13/18 ration i not gonna do it....no time...u proof yrself
  
  ahahhahahahha
  
  
• saline

  6 Apr 06, 12:58

  your cousin is in primary 6?
  think such questions are there to spot the gifted kids....
• HENG@

  6 Apr 06, 13:08

  Originally posted by newcomer:

  Mr Koh's salary to that of his wife is in the ratio 4:3. Each of them saves $246 and spends the rest of their money. If Mr Koh's expenditure to that of his wife is in the ratio 18:13, find their total salaries.
  
  Any help would be much appreciated.
  
  P.S: Kind of embarrassed to not able to solve this qns for my little cousin.

  Hmm... the method Ive used isn't primary sch method. They've gotta be kidding if they give them questions like these in pri sch nowadays
  
  Anyways here the working:
  
  Let Mr Koh's expenditure be x, Mrs Koh's expenditure be y
  
  therefore:
  
  x = 18
  y .. 13
  
  hence:
  x = 18y
  ...... 13
  
  we also know that:
  
  (x+246) = 4
  (y+246) .. 3
  
  hence:
  (3x + 73 = (4y + 984) --------- equation 1
  
  sub x into equation 1:
  
  54y + 738 = 4y + 984
  13
  
  54y - 52y = 246
  13 .. 13
  
  2y = 246
  13
  
  2y = 3198
  
  y = 1599
  
  from y:
  x = 18y
  ...... 13
  
  x = (18 x 1599)/13
  
  x = 2214
  
  hence total salary: 2214 + 1599 + 2(246) = 4305
• digicharat

  6 Apr 06, 13:18

  my headache is coming back...
• sohguanh

  6 Apr 06, 13:23

  If I'm not wrong, during my education times usually such problem are solved using algebra. However during my younger sister education times, it seem to have changed. The teachers are teaching them a new way of tackling such problems. It involve drawing of diagram and tables and it is actually much faster and easier for kids to visualize compared to algebra.
  
  I guess for primary kids, algebra are too deep for them. They should be using the diagram and tables they are taught to solve such problems.
  
  Btw, I still dunno the new way of solving such problems. Me belong to the old school of teachings. It will be ideal more for kids to learn the diagram and tables now and then later when in secondary school learn the algebra method.
  
  
• SGpork

  6 Apr 06, 13:24

  wa piang eh