Sagot :
Bonjour,
A)
priorité à la multiplication
5/8 * 3/10 = 15/80
La soustraction : même dénominateur
21/8 = 210/80
210/80 -15/80 = 195/80
On simplifie : (tout diviser par 5)
39/16
B)
multiplication:
9/10 *5/21= 45/210
mêm dénominateur
1/2 = 210/420
addition:
210/420 + 45 /210 = 255/210
simplification:
51/42 = 17/14
C)
division ( on multiplie par l'inverse)
5/12 * 9/10 = 45/120
addition:
15/4 + 45/120 =
même dénominateur
450/120 + 45/120 = 495/120 = 99/24 =33/8
D)
Multiplication
5*9/10 = 45/10
45/10 -7/10 =38/10 = 19/5
bonjour
A=21/8-5/8x3/10
=21/8-3/16
=(21x2)/(8x2)-3/16
=42/16-3/16
=39/16
B=1/2+9/10x5/21
=1/2+3/14
=(7x1)/(2x7)+3/14
=7/14+3/14
= 10/14
=(5x2)/(7x2)
=5/7
C=15/4+5/12÷10/9
= 15/4+5/12x9/10
=15/4+3/8
=(15x2)/(4x2)+3/8
=30/8+3/8
=33/8
D=5x9/10-7/10
=(5x9)/(1x10)-7/10
=45/10-7/10
=38/10
=(19x2)/(5x2)
=19/5