Toán Lớp 6: Bài 4. Tính theo hai cách:
a) 18 . 15 – 3 . 6 . 10 ; b) 63 – 9 . (12 + 7) ;
c) 39 . (29 – 13) – 29 . (39 – 13)
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Toán Lớp 6: Bài 4. Tính theo hai cách:
a) 18 . 15 – 3 . 6 . 10 ; b) 63 – 9 . (12 + 7) ;
c) 39 . (29 – 13) – 29 . (39 – 13)
Comments ( 1 )
a)
** Cách 1:
18.15-3.6.10
=270-18.10
=270-180
=90
** Cách 2:
18.15-3.6.10
=18.15-18.10
=18.(15-10)
=18.5
=90
$\\$
b)
** Cách 1:
63-9.(12+7)
=63-9.19
=63-171
=-108
** Cách 2:
63-9.(12+7)
=63-9.12+9.7
=63-108+63
=(63-63)-108
=-108
$\\$
c)
** Cách 1:
39.(29-13)-29.(39-13)
=39.29-39.13-29.39+29.13
=(39.29-29.39)+(29.13-39.13)
=0+13.(29-39)
=13.(-10)
=-130
$\\$
** Cách 2:
39.(29-13)-29.(39-13)
=39.16-29.26
=624-754
=-130