Toán Lớp 6: Tính một cách hợp lí:
a) (125).(-134).(-8);
b) 12.(-27) + 12.(-73);
c) 4.(1 930 + 2 019) + 4.(-2 019).
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Toán Lớp 6: Tính một cách hợp lí:
a) (125).(-134).(-8);
b) 12.(-27) + 12.(-73);
c) 4.(1 930 + 2 019) + 4.(-2 019).
Comments ( 2 )
\text{= [125 . (-8)] . (-134)}
$\text{= (-1000) . (-134)}$
$\text{= 134 000}$
$\text{b) 12 . (-27) + 12 . (-73)}$
$\text{= 12 . [(-27) + (-73)]}$
$\text{= 12 . (-100)}$
\text{= – 1 200}
$\text{c) 4 . (1 930 + 2 019) + 4 . (-2 019)}$
\text{= 4.1 930 + 4 . 2 019 + 4 . (-2 019)}
$\text= 4 . 1 930 + [4 . 2 019 + 4 . (-2 019)]{}$
$\text{= 4 . 1 930 + 4 .[2019 + (-2 019)]}$
$\text{= 4 . 1 930 + 4 . 0}$
$\text{= 7 720}$
= [125.(-8)].(-134)
= (-1000).(-134)
= 134 000.
b) 12.(-27) + 12.(-73)
= 12.[(-27) + (-73)]
= 12. (-100)
= – 1 200.
c) 4.(1 930 + 2 019) + 4.(-2 019)
= 4.1 930 + 4.2 019 + 4.(-2 019)
= 4.1 930 + [4.2 019 + 4.(-2 019)]
= 4.1 930 + 4.[2019 + (-2 019)]
= 4.1 930 + 4.0
= 7 720.