Bonjour
Calculer et donner le résultat sous la forme d'une fraction simplifiée :
a. 27/28 + 3/4
= 27/28 + (3 x 7) / (4 x 7)
= 27/28 + 21/28
= 48/28
= (4 x 12) / (4 x 7)
= 12/7
b. 25/14 - 30/42
= (25 x 3) / (14 x 3) - 30/42
= 75/42 - 30/42
= 45/42
= (3 x 15) / (3 x 14)
= 15/14
c. 25/36 - 2/3
= 25/36 - (2 x 12) / (3 x 12)
= 25/36 - 24/36
= 1/36
d. 39/40 - 4/5
= 39/40 - (4 x 8) / (5 x 8)
= 39/40 - 32/40
= 7/40.
