calculer en utilisant la distributivité: 99 x 77 22,5 x 999

(100-1)*77
=77*(100-1)
=77*100+77*(-1)
=7700-77
=7623

22.5*(1000-1)
=22.5*1000+22.5*(-1)
=22500-22.5
=22477.5

voilà :)

99*77=7632
22.5*999=22477.5