Explicație pas cu pas:
a. 35x99=35x(100-1)=35x100-35x1=3500-35 =3465
b.
27x101=27x(100+1)=27x100+27x1=2700+27=2727
c.
15x102=15x(100+2)=15x100+15x2=1500+30=1530
d.
31x98=31x(100-2)=31x100-31x2=3100-62 =3038
e.
4x999=4x(1000-1)=4x1000-4x1=4000-4 =3996
f.
5x1004=5x(1000+4)=5x1000+5x4 =5000+20=5020
