Toán Lớp 6: Bài 2:Tính nhanh,tính hợp lí
a) (2100 – 42) : 21
b)2 . 31 . 12 + 4 . 6 . 42 + 8 . 27
c)15 . 2^3 – 3^2 . 8
d)24 . 76 +23 . 24 + 24
e)256: (17 . 2^3 + 15 . 2^3)
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Toán Lớp 6: Bài 2:Tính nhanh,tính hợp lí
a) (2100 – 42) : 21
b)2 . 31 . 12 + 4 . 6 . 42 + 8 . 27
c)15 . 2^3 – 3^2 . 8
d)24 . 76 +23 . 24 + 24
e)256: (17 . 2^3 + 15 . 2^3)
Comments ( 2 )
a) (2100 – 42) : 21
=2100:21-42:21
=100-2
=98
b)2 . 31 . 12 + 4 . 6 . 42 + 8 . 27
=31.24+24.42+24.9
=(31+9+42).24
=82.24
=1968
c)c)15 . 2^3 – 3^2 . 8
=15.2^3-3^2. 2^3
=2^3(15-3^2)
=8.(15-9)
=8.6
=48
d) 24 . 76 +23 . 24 + 24
=24.(76+23+1)
=24.100
=2400
e)256: (17 . 2^3 + 15 . 2^3)
=256:[2^3(17+15)]
=256:(8.32)
=256:256
=1