Question

Tính hợp lí

1/ 45. 18 – 5. 9. 28

2/ 54 – 6. (12 + 9)

3/ 23. (16 – 5) – 16. (23 - 5)

4/ 29. (2019 – 13) – 2019. (29 – 13)

5/ 31. (-18) + 31. ( - 80) – 31.2

6/ (-12).48 + (-12). 51 + (-12)

Answer 1

1/ \(45.18-5.9.28\\ =45.18-45.28\\ =45.\left(18-28\right)\\ =45.\left(-10\right)=-450\)

2/\(54-6.\left(12+9\right)\\ =6.\left(9-12-9\right)\\ =6.\left(-12\right)\\ =-72\)

3/ \(23.\left(16-5\right)-16.\left(23-5\right)\\ =23.16-23.5-16.23+16.5\\ =5.\left(-23+16\right)\\ =5.\left(-7\right)=-35\)

4, \(29.\left(2019-13\right)-2019.\left(29-13\right)\\ =29.2019-29.13-29.2019+13.2019\\ =13.\left(-29+2019\right)\\ =13.1990=25870\)

5/\(31.\left(-18\right)+31.\left(-80\right)-31.2\\ =31.\left[\left(-18\right)+\left(-80\right)-2\right]\\ =31.\left(-100\right)\\ =-3100\)

6/ \(\left(-12\right).48+\left(-12\right).51+\left(-12\right)\\ =\left(-12\right).\left(48+51+1\right)\\ =\left(-12\right).100\\ =-1200\)

Answer 2

1/ 45. 18 – 5. 9. 28

= 45 . 18 – 45 . 28

= 45 . (18 - 28)

= 45 . (-10)

= -450

2/ 54 – 6. (12 + 9)

= 54 – (6 . 12 + 6 . 9)

= 54 – 6 . 12 - 6 . 9

= 54 - 6 . 9 – 6 . 12

= 54 - 54 - 72

= 0 - 72

= -72

3/ 23. (16 – 5) – 16. (23 - 5)

= (23 . 16 – 23 . 5) – (16 . 23 - 16 . 5)

= 23 . 16 – 23 . 5 – 16 . 23 + 16 . 5

= (23 . 16 – 16 . 23) + (-23 . 5 + 16 . 5)

= (23 . 16 – 16 . 23) + 5 . (-23 + 16)

= 0 + 5 . (-7)

= 5 . (-7)

= -35

4/ 29. (2019 – 13) – 2019. (29 – 13)

= (29. 2019 – 29 . 13) – (2019. 29 – 2019 . 13)

= 29. 2019 – 29 . 13 – 2019. 29 + 2019 . 13

= (29 . 2019 - 2019 . 29) + (2019 . 13 - 29 . 13)

= (29 . 2019 - 2019 . 29) + 13 . (2019 - 29)

= 0 + 13 . 1990

= 0 + 25870

= 25870

5/ 31. (-18) + 31. ( - 80) – 31.2

= 31 . [(-18) + (-80) - 2]

= 31 . (-100)

= -3100

6/ (-12) . 48 + (-12) . 51 + (-12)

= (-12) . 48 + (-12) . 51 + (-12) . 1

= (-12) . (48 + 51 + 1)

= (-12) . 100

= -1200