Question

Calculati,dupa modelul prezentat: 12x99=12x(100-1)=12x100-12x1=1200-12=1188 a)35x99 b)27x101 c)15x102 d)31x98 e)4x999 f)5x1004

Answer 1

a)35×99=35×(100-1)=35×100-35×1
=3500-35=3465
b)27×101=27×(100+1)=27×100+27×1
=2700+27=2727
c)15×102=15×(100+2)=15×100+15×2
=1500+30=1530
d)31×98=31×(100-2)=31×100-31×2
=3100-62=3038
e)4×999=4×(1000-1)=4×1000-4×1
=4000-4=3996
f)5×1004=5×(1000+4)=5×1000+5×4
=5000+20=5020

Answer 2

a)   35 × 99 = 35 × ( 100 - 1 ) = 35 × 100 - 35 × 1 = 3 500 - 35 = 3 465

b)   27 × 101 = 27 × ( 100 + 1 ) = 27 × 100 + 27 × 1 = 2 700 + 27 =  2 727

c)   15 × 102 = 15 × ( 100 + 2 ) = 15 × 100 + 15 × 2 = 1 500 + 30 = 1 530

d)   31 × 98 = 31 × ( 100 - 2 ) = 31 × 100 - 31 × 2 = 3 100 - 62 = 3 038

e)   4 × 999 = 4 × ( 1 000 - 1 ) = 4 × 1000 - 4 × 1 = 4 000 - 4 = 3 996

f)    5 × 1 004 = 5 × ( 1 000 + 4 ) = 5 × 1000 + 5 × 4 = 5 000 + 20 = 5 020