P5 Math: Cookies

Every child was given 2 bags of cookies. Each bag contained either 10 chocolate cookies or 15 butter cookies. There were 88 children and they received 2345 cookies altogether. How many butter cookies did the children receive?

There are two extreme cases for minimum and maximum number of cookies for the children.

1. Minimum: each bag consists of chocolate cookies
   So, total = 88 x (10 + 10) = 1760 cookies
2. Maximum:  each bag consists of butter cookies
   So, total = 88 x (15 + 15) = 2640 cookies

From the extreme cases above, the total 2345 cookies should come from mix number of cookies bag, not a same cookies. 

• Use assumption maximum (2), it means there are extra 2640 - 2345 = 295 cookies than received.
• The difference number of cookies between maximum type to mix cookies = (2x15) - (10+15) = 5
• So there must be 295 / 5 = 59 children are holding mix number of cookies bag.
• It means 29 children has two bags of butter cookies while 59 children holds mix number of cookies bag.
• Number of butter cookies received = 29x(15+15) + (59x15) = 1755

Check:

Number of butter cookies = 1755

Number of chocolate cookies = 59 x 10 = 590

Total = 1755 + 590 = 2345 cookies.