Question

[Cao Thị Thùy Dương]

6.Tính bằng cách thuận tiện nhất:

a) 1/10+ 2/20 + 3/30 + 4/40 + 5/50 + 6/60 + 7/70 + 8/80 + 9/90

=...............................................................................................................................................................................................

=...............................................................................................................................................................................................

b) 3,72 + 2,05 + 6,28 + 7,95 =....................................................................................................................................................

                                          =....................................................................................................................................................

Answer 1

[Lâm liên quân]

b) (3,72+6,28)+(2,05+7,95)

=10+10

=20

Answer 2

[Linh 2k5]

a)

\(\frac{1}{10}+\frac{2}{20}+...+\frac{8}{80}+\frac{9}{90}\) = \(\frac{1}{10}+\frac{1}{10}+...+\frac{1}{10}+\frac{1}{10}\)(rút gọn )

                                                    = 9.\(\frac{1}{10}\)= \(\frac{9}{10}\)

b)= ( 3,72+6,28 ) +( 2,05 +7,95) =10+10 = 20.