Question

Tính bằng cách hợp lí

35 . 18 - 5 . 7 . 28

45 - 5 . (12 + 9)

24 . (16 - 5) - 16. (24 - 5)

Answer 1

35.18-5.7.28=35.18-35.28=35(18-28)=-350

45-5.12-5.9=45-60-45=-60

=24.16-24.5-16.24-16.5=5(-24-16)=5.-40=-200

Answer 2

 35 . 18 - 5 . 7 . 28 = 35 . 18 - 35 . 28

= 35 . (18 - 28)

= 35 . (-10)

= -350

45 - 5 . (12 + 9) = 45 - 5 . 9 + 5 . 12

= 45 - 45 + 60

= 60

24 . (16 - 5) - 16 . (24 - 5) = 24 . 16 - 24 . 5 - 16 . 24 + 16 . 5

= (24 . 16 - 16 . 24) + (16 . 5 - 24 . 5)

=0 + 5 . (16 - 24)

= 5. (-8)

= -40