Réponses

2014-03-03T19:09:36+01:00
1) 
42/840 = 42 x 1/42 x 20 = 1/20
12/80 = 4 x 3/4 x 20 = 4/20
21/70 = 7 x 3/7 x 10 = 3/10
56/800 = 8 x 7/8 x 100 = 7/100
39/150 = 3 x 13/3 x 50 = 13/50
5/250 = 5 x 1/5 x 50 = 1/50
90/600 = 30 x 3/30 x 20 = 3/20

2)
1/20 = 1 x 5/5 x 20 = 5/100
4/20 = 4 x 5/5x 20 = 20/100
3/10 = 3 x 10/10 x 10 = 30/100
7/100 = 7/100
13/50 = 13 x 2/50 x 2 = 26/100
1/50 = 2 x 1/50 x 2 = 2/100
3/20 = 3 x 5/20 x 5 = 15/100

3)
2/100 < 5/100 < 7/100 < 15/100 < 20/100 < 26/100 < 30/100

J'espère t'avoir aidé! :)