Bonjour
1/5 de 20 => 1/5 x 20 = 20/5 = (5 x 4)/5 = 4
1/4 de 120 => 1/4 x 120 = 120/4 = (30 x 4)/4 = 30
1/8 de 40 => 1/8 x 40 = 40/8 = (5 x 8)/8 = 5
exercice 2 :
2/3 de 45€
= 2/3 x 45
= 45/3 x 2
= (3 x 15)/3 x 2
= 15 x 2
= 30 €
3/4 de 16 min
= 3/4 x 16
= 16/4 x 3
= (4 x 4)/4 x 3
= 4 x 3
= 12 min
5/7 de 49 cL
= 5/7 x 49
= 49/7 x 5
= (7 x 7)/7 x 5
= 7 x 5
= 35 cL
13/11 de 44 kg
= 13/11 x 44
= 44/11 x 13
= (4 x 11)/11 x 13
= 4 x 13
= 52 kg
5/6 de 36 g
= 5/6 x 36
= 36/6 x 5
= (6 x 6)/6 x 5
= 6 x 5
= 30 g
6/8 de 28 élèves
= 6/8 x 28
= (2 x 3)/(2 x 4) x 28
= 3/4 x 28
= 28/4 x 3
= (7 x 4)/4 x 3
= 7 x 3
= 21 élèves
Exercice 3 :
bus de 54 places, 7/9 des sièges sont occupés. Combien y a t il de passagers ?
= 7/9 x 54
= 54/9 x 7
= (6 x 9)/9 x 7
= 6 x 7
= 42 sièges occupés
