PSLE
Kathy baked some cookies. She gave ¹₂ of the cookies to her relatives and 48 to her friends. She was left with ⁷₂₀ of the cookies. She packed these into 11 boxes. Some boxes contained 7 cookies while the rest contained 12 cookies.

1. How many cookies were packed into the 11 boxes?
2. How many boxes contained 12 cookies?

(a)
Fraction of the cookies given to her friends
= 1 - ¹₂ - ⁷₂₀

= 1 - ¹⁰₂₀ - ⁷₂₀
= ³₂₀

Number of cookies that Kathy gave to her friends = 3 u

3 u = 48

1 u = 48 ÷ 3 = 16

Number of cookies that were packed in 11 boxes
= 7 u
= 7 x 16
= 112

Number of cookies that were packed in 11 boxes = 112

Boxes of 12	Cookies	Boxes of 7	Cookies	Total cookies
11	132	0	0	132
10	120	1	7	127

If all the cookies are packed in boxes of 12, the number of cookies needed
= 11 x 12
= 132

Small difference
= 132 - 127
= 5

Big difference
= 132 - 112
= 20

Number of boxes of 7 cookies 
= 20 ÷ 5
= 4

Number of boxes of 12 cookies
= 11 - 4
= 7

Answer(s): (a) 112; (b) 7