Bonjour,

25 = 5 × 5

125 = 5 × 5 × 5

donc 25/125 = (5×5)/(5×5×5) = 1/5

456 ÷ 2 = 228

228 ÷ 2 = 114

114 ÷ 2 = 57

57 ÷ 3 = 19

donc 456 = 2 × 2 × 2 × 3 × 19

2 016 ÷ 2 = 1 008

1 008 ÷ 2 = 504

504 ÷ 2 = 252

252 ÷ 2 = 126

126 ÷ 2 = 63

63 ÷ 3 = 21

21 ÷ 3 = 7

donc 2016 = 2 × 2 × 2 × 2 × 2 × 3 × 3 × 7

donc 2016/456 = (2×2×2×2×2×3×3×7)/(2×2×2×3×19)

                         simplification par les chiffres soulignés

                        = (2×2×3×7)/19

                        = 84/19