P5 maths question

• Helengoo

  7 Jun 12, 18:13

  Keith went shopping with thrice as many S$5 notes as S$2 notes . After he used 28 pieces of S$5 notes , he had 5 times as many S$2 notes as S$5 notes left . Find the total value of his remaining S$5 and S$2 notes .

   

  Thanks

• lolerchild

  7 Jun 12, 23:49

  I would suggest using a model to better illustrate the problem.

  But here's the algebra method

  let original no. of $5 notes be x

  let original no. of $2 notes be 1/3 x

  5(x-28) = 1/3 x

  15(x-28) = x

  14x = 420

  x = 30

  value of remaining $5 notes = (30-28) * 5 = $10

  value of remaining $2 notes = (30/3) * 2 = $20

  Total value= $30

• Helengoo

  8 Jun 12, 19:27

  Hi Lolerchild ,

  Thanks for your reply . However , I need the answer shown in model method . Need your assistance .

   

  Regards .

   

   

   

• lolerchild

  9 Jun 12, 02:59

  

  as you can see,

  in the beginning you have 3 times as many $5 as $2.

  After using 28 notes of $5, you are left with 5 times as much $2 as $5.

  Hence 

  14 blocks = 28 notes.

  1 block = 2 notes

  remaining $5 notes= 1*2 (2*$5=$10)

  remaining $2 notes= 5*2 (10*2=$20)

  total remaining=$30