PSLE
Erika baked some muffins. She gave ¹₁₀ of the muffins to her friends and 84 to her students. She was left with ¹₂ of the muffins. She packed these into 17 boxes. Some boxes contained 5 muffins while the rest contained 7 muffins.

1. How many muffins were packed into the 17 boxes?
2. How many boxes contained 7 muffins?

(a)
Fraction of the muffins given to her students
= 1 - ¹₁₀ - ¹₂

= 1 - ¹₁₀ - ⁵₁₀
= ⁴₁₀

Number of muffins that Erika gave to her students = 4 u

4 u = 84

1 u = 84 ÷ 4 = 21

Number of muffins that were packed in 17 boxes
= 5 u
= 5 x 21
= 105

Number of muffins that were packed in 17 boxes = 105

Boxes of 7	Muffins	Boxes of 5	Muffins	Total muffins
17	119	0	0	119
16	112	1	5	117

If all the muffins are packed in boxes of 7, the number of muffins needed
= 17 x 7
= 119

Small difference
= 119 - 117
= 2

Big difference
= 119 - 105
= 14

Number of boxes of 5 muffins 
= 14 ÷ 2
= 7

Number of boxes of 7 muffins
= 17 - 7
= 10

Answer(s): (a) 105; (b) 10