Question

Tính nhanh :

399x45 + 22x399

                                       

1995x1996 - 1991x1995

 

Answer 1

399x45+22x399

=399x(45+22)

=399x67

=26733

1995x1996-1991x1995

=1995x(1996-1991)

=1995x5

=9975

Answer 2

\(\frac{399\times45+22\times399}{1995×1996+1991×1995}=\frac{399\times(45+22)}{1995×\left(1996+1991\right)}=\frac{399\times67}{1995×3987}=\frac{67}{19935}\)