Question

3.Tính hợp lí

a, 21.35-3.25.7

b, 77-11.(30+7)

c, 85.(35-27)-35.(85-27)

d, 47.(45-15)-47.(45+15)

Answer 1

a, 21.35-3.25.7=21.35-21.25=21.(35-25)=21.10=210

b, 77-11.(30+7)=77-330-77=-330

c, 85.(35-27)-35.(85-27)=85.35-85.27-35.85+35.27=0

d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-2(47.15)=1410

Answer 2

a, 21.35-3.25.7=21.35-21.25=21.10=210

b,77-11.(30+7)=77-11.30-11.7=-11.30=-330

c,85.(35-27)-35.(85-27)=85.35-85.27-85.35+35.27=27.(-50)=-1350

d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-47.30=-1410

Answer 3

a, 21 . 35 - 3 . 25 . 7

= (21 . 35) - (3 . 25 . 7)

= 735 - 525

= 210

b, 77-11.(30+7)

= 77 - 11.30 - 11.7

= -11.30

= -330

c, 85.(35-27)-35.(85-27)

= 85.35 - 85.27 - 85.35 + 35.27

= 27.(-50)

= -1350

d, 47.(45-15)-47.(45+15)

= 47.45 - 47.15 - 47.45 - 47.15

= -47.30

= -1410