PSLE
Mary baked some shortbreads. She gave ¹₅ of the shortbreads to her friends and 78 to her students. She was left with ¹₂ of the shortbreads. She packed these into 14 boxes. Some boxes contained 7 shortbreads while the rest contained 11 shortbreads.

1. How many shortbreads were packed into the 14 boxes?
2. How many boxes contained 11 shortbreads?

(a)
Fraction of the shortbreads given to her students
= 1 - ¹₅ - ¹₂

= 1 - ²₁₀ - ⁵₁₀
= ³₁₀

Number of shortbreads that Mary gave to her students = 3 u

3 u = 78

1 u = 78 ÷ 3 = 26

Number of shortbreads that were packed in 14 boxes
= 5 u
= 5 x 26
= 130

Number of shortbreads that were packed in 14 boxes = 130

Boxes of 11	Shortbreads	Boxes of 7	Shortbreads	Total shortbreads
14	154	0	0	154
13	143	1	7	150

If all the shortbreads are packed in boxes of 11, the number of shortbreads needed
= 14 x 11
= 154

Small difference
= 154 - 150
= 4

Big difference
= 154 - 130
= 24

Number of boxes of 7 shortbreads 
= 24 ÷ 4
= 6

Number of boxes of 11 shortbreads
= 14 - 6
= 8

Answer(s): (a) 130; (b) 8