Question

Calculeaza,aproximand intai convenabil numerele:9;99;999;101;1.001;10.001.
Model 1:
854×99=854×(100-1)=854×100-854=85.400-854=84.546
Model 2:
632×9.999=632×(10.000-1)=6.320.000-632=6.319.368

Answer 1

854x9=854x(10-1)=854x10-854x1=8540-854 = 7.686
854×99=854×(100-1)=854×100-854=85.400-854=84.546
854x999=854x(1000-1)=854x1000-854x1=854.000-854=853.146
854x101=854x(100+1)=854x100+854x1=85.400+854=86.254
854x1.001=854x(1000+1)=854x1000+854x1=854.000+854=854.854
854x10.001=854x(10.000+1)=854x10.000+854x1=8.540.000+854=8.540.854

632x9=632x(10-1)=632x10-632x1=6320-632 = 5.688
632×99=632×(100-1)=632×100-632=63.200-632=62.568 632x999=632x(1000-1)=632x1000-632x1=632.000-632=631.368 632x101=632x(100+1)=632x100+632x1=63.200+632=63.832 632x1.001=632x(1000+1)=632x1000+632x1=632.000+632=632.632 632x10.001=632x(10.000+1)=632x10.000+632x1=6.320.000+632=6.320.632