Bonjour,
a. 1,2/5 x 3,5/2
= 4,2/10
= (4,2 x 10) / (10 x 10)
= 42/100
= (2 x 21) / (2 x 50)
= 21/50.
b. 5,2/7 x 1,5/4
= 7,8/28
= (7,8 x 10) / (28 x 10)
= 78/280
= (2 x 39) / (2 x 140)
= 39/140
c. 4,1/3 x 8/2,2
= 32,8/6,6
= (32,8 x 10) / (6,6 x 10)
= 328/66
= (2 x 164) / (2 x 33)
= 164/33.