Question

119 / TÍNH BẰNG HAI CÁCH 

A /  15.12-3.5.10         B / 45-9.(13+5)       C / 29.( 19-13)-19.(29-13)

Answer 1

a. C1: 15.12 - 3.5.10

= 15.12 - 15.10

= 15. (12 - 10)

= 15. 2

= 30

C2: 15.12 - 3.5.10

= 180 - 150

= 30

b. C1: 45 - 9.(13+5)

= 9.5 - 9.(13+5)

= 9.[5-(13+5)]

= 9.(5-13-5)

= 9.(-13)

= -117

C2: 45 - 9.(13+5)

= 45 - 9.18

= 45 - 162

= -117

c. C1: 29.(19-13) - 19.(29 - 13)

= 29.19 - 29.13 - 19.29 + 19.13

= 19.13 - 29.13

= (19-29).13

= -10.13

= -130

C2: 29.(19-13)-19.(29-13)

= 29.6-19.16

= 174 - 304

= -130

Answer 2

a) 15.12 - 3.5.10

= 15.12 - 15.10

= 15.(12-10)

= 15.2 = 30 

Answer 3

chung may hoc ngu vai

Answer 4

A=30  100%

Answer 5

a)

Cách 1: 15 . 12 – 3 . 5 . 10 = 180 – 150 = 30.

Cách 2: 15 . 12 – 3 . 5 . 10 = 15 . 12 – 15 . 10 = 15 . (12 – 10) = 15 . 2 = 30

b)

Cách 1: 45 – 9 . (13 + 5) = 45 – 9 . 18 = 45 – 162 = –117.

Cách 2: 45 – 9 . (13 + 5)

= 9 . 5 – (9 . 13 + 9 . 5)

= 9 . 5 – 9 . 13 + 9 . 15

= –9 . 13 = –117.

Answer 6

c)

Cách 1: 29 . (19 – 13) – 19 . (29 – 13) = 29 . 6 – 19 . 16 = 174 – 304 = –130.

Cách 2: 29 . (19 – 13) – 19 . (29 – 13)

= 29 . 19 – 29 . 13 – (19 . 29 – 19 . 13)

= 29 . 19 – 29 . 13 – 19 . 29 + 19 . 13

= 19 . 13 – 29 . 13 = 13 . (19 – 29) = 13 . (–10) = –130.

Answer 7

a) Cách 1:

15.12-3.5.10

= 180-15.10

= 180-150

= 30

Cách 2:

15.12-3.5.10

= 15.12-15.10

= 15.(12-10)

= 15.2

= 30

b) Cách 1:

45-9.(13+5)

= 45-9.18

= 45-162

= -117

Cách 2:

45-9.(13+5)

= 45-9.13+9.5

= 45-117+45

= [45+(-45)] -117

= 0-117

= -117

c) Cách 1:

29.(19-13)-19.(29-13)

= 29.6-19.16

= 174-304

= -130

Cách 2:

29.(19-13)-19.(29-13)

= 29.19-29.13-19.29-19.13

= 19.13-29.13

= (19-29).13

= -10.13

= -130