PSLE
Xandra baked some cookies. She gave ¹₈ of the cookies to her relatives and 66 to her friends. She was left with ¹₂ of the cookies. She packed these into 10 boxes. Some boxes contained 7 cookies while the rest contained 10 cookies.

1. How many cookies were packed into the 10 boxes?
2. How many boxes contained 10 cookies?

(a)
Fraction of the cookies given to her friends
= 1 - ¹₈ - ¹₂

= 1 - ¹₈ - ⁴₈
= ³₈

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

3 u = 66

1 u = 66 ÷ 3 = 22

Number of cookies that were packed in 10 boxes
= 4 u
= 4 x 22
= 88

Number of cookies that were packed in 10 boxes = 88

Boxes of 10	Cookies	Boxes of 7	Cookies	Total cookies
10	100	0	0	100
9	90	1	7	97

If all the cookies are packed in boxes of 10, the number of cookies needed
= 10 x 10
= 100

Small difference
= 100 - 97
= 3

Big difference
= 100 - 88
= 12

Number of boxes of 7 cookies 
= 12 ÷ 3
= 4

Number of boxes of 10 cookies
= 10 - 4
= 6

Answer(s): (a) 88; (b) 6