pri 3 maths

• Chunghong2004

  10 May 12, 15:49

  Can someone help me with a pri 3 question?
  

  
  

  The average score of all children in the class for a test was 70 marks. The average score of the 15 girls was 77 marks. The average score of the boys was 65 marks. How many boys are there in the class?
  a) 15
  b) 18
  c) 21
  d) 23
  So what is the answer and how it is done? thanks
  

• FireIce

  10 May 12, 16:19

  avg is p5
• Summer hill

  15 May 12, 20:01

  Sad to say, I can't even solve it.

  I remember my primary school life is about fractions and counting cubes, measuring area. 

• charlize

  15 May 12, 20:04

  Since it is MCQ just sub the 4 answers and see which one fits lor .

• LemonRay

  27 May 12, 21:08

  Total marks of all the girls

  77 x 15  = 1155

   

  Avg score of all children

  Let y be the number of boys

  (1155 + 65y)/15+y = 70

  1155 + 65y = 1050 + 70y

  105 = 5y

  y = 21

• Summer hill

  27 May 12, 22:13

  Originally posted by LemonRay:

  Total marks of all the girls

  77 x 15  = 1155

   

  Avg score of all children

  Let y be the number of boys

  (1155 + 65y)/15+y = 70

  1155 + 65y = 1050 + 70y

  105 = 5y

  y = 21

  primary school cannot use algrebra!

• LemonRay

  28 May 12, 00:12

  Other than algebra, what can I use ? =="

  Just learn in advance also can ... ALL ARE MATH!

• charlize

  28 May 12, 00:16

  Originally posted by LemonRay:

  Other than algebra, what can I use ? =="

  Just learn in advance also can ... ALL ARE MATH!

  Good luck explaining algebra to a p3 kid. 

• FireIce

  28 May 12, 00:29

  77 - 70 = 7

  7 x 15 = 105 

  70 - 65 = 5

   

  105/5 = 21

   

   

  21 boys

• Summer hill

  28 May 12, 10:09

  Originally posted by charlize:

  Good luck explaining algebra to a p3 kid. 

  algrebra is the most challenging thing in mathematics....

  you mastered it can go advanced, which is algrebra again. 

  What's the use of learning?  Algrebra cannot apply to real life.  

  We should learn how much money is needed to buy HDB. 

• FireIce

  28 May 12, 12:10

  algebra is just using alpahbets to represent a value

   

  if u dont like it, u can always change to using bananas and elephants to represent