Question

Tính nhanh:

399x45+55x399 / 1995x1996-1991x1995

Answer 1

399 x 45 + 55 x 399 / 1995 x 1996 - 1991 x 1995

= 399 x (45 + 55) / 1995 x (1996 - 1991)

= 399 x 100 / 1995 x 5=399 x 100/ 399 x 5 x 5

= 399 x 100/399 x 25

=100/25 = 4