primary 5 math problem sum

• shristine

  18 Mar 11, 14:02

  need some help here. since it's a p5 problem sum, no algebra can be used. other than trial and error, what are the other methods.

   

  Question:

  There are 50 children. Each boy eats 10 cookies. Each girl eats 7 cookies. All the girls ate 44 more cookies than all the boys. How many more girls than boys are there?

  Ans: 32 girls, 18 boys, 14 more girls than boys.

  I managed to work out this way:

  Assuming all the children are boys,

  50*10 = 500

  500 +44=544 (no. of girls)

  Then, to find number of girls,

  I take 544/17 = 32.

  However, i do not understand why i should divide it by 17 and not 7.

  Thanks for looking and for your help. :)

• Nelstar

  18 Mar 11, 14:24

  Assuming all girls ate the boys' share and ate 44 more. That will give you 544 cookies.

  Since they are eating the boy's cookies, the girls ate 17 cookies each.

  So the number of girls is 544/17.

  

• normalguy87

  18 Mar 11, 23:20

  Here's another way to look at the problem.

  Girls   Boys    Difference

  0        50        0(7) - 50(10) = -500

  1        49        1(7) - 49(10) = -483 (= -500 +17) 

  As noticed, every exchange between a girl and boy makes a difference of 17 in the difference of no. of cookies eaten btw the girls and boys.

  Since the question stated that girls ate 44 more than boys, the difference in no. of cookies eaten must increase by 544 from -500, in order to reach +44.

  Therefore,

  +17 -> additional 1 girl

  +544 -> additional 32 girls

  If the negative 500 is hard to explain becuz primary ain't taught negative numbers yet, can start with 50 girls 0 boys.

• cubsarecute

  14 Apr 11, 23:04

  Another problem sum.. thks in advance =)

  Alan had 2/3 as many stickers as Bob. After Alan bought another 8 stickers and Bob lost 5 stickers, Alan now had 4/5 as many stickers as Bob. Find the number of stickers Alan and Bob had at first.