A=
3/70*35/18
= 3*35/70*18
= 3*35/35*2*6*3
les 3 et les 35 se simplifient
=1/12
B=
27/28 * 14/45
= 27*14/28*45
= 3*9*7*2/4*7*9*5
=3*2/4*5
=3*2/2*2*5
=3/10
C=
42/18 * 27/140
= 42*27/18*140
= 7*6*9*3/6*3*7*2*10
=9/20
D=
40/16*48
= 40/16*48/1
= 40*48/16*1
= 20*2*6*8/8*2
=20*6
=120