Toán Lớp 4: Tính bằng cách thuận tiện
a , ( 145 x 99 + 145 ) – ( 143 x 101 – 143 )
b , 20x 190 x 50
c, 769 x 85 -769 x 75
d , 1994 x 867 + 1995 x 133
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Toán Lớp 4: Tính bằng cách thuận tiện
a , ( 145 x 99 + 145 ) – ( 143 x 101 – 143 )
b , 20x 190 x 50
c, 769 x 85 -769 x 75
d , 1994 x 867 + 1995 x 133
Comments ( 2 )
a) ( 145 × 99 + 145 ) – ( 143 × 101 – 143 )
= ( 145 × 99 + 145 × 1 ) – ( 143 × 101 – 143 × 1)
= 145 × ( 99 + 1) – ( 143 × 101 – 1)
= 145 × 100 – 143 × 100
= 14 500 – 14 300
$\text{= 200}$
b) 20 × 190 × 50
= ( 20 × 50 ) × 190
= 1000 × 190
$\text{= 190 000}$
c) 769 × 85 -769 × 75
= 769 × ( 85 – 75 )
= 769 × 10
$\text{= 7690}$
d) 1994 × 867 + 1995 × 133
= 1994 × 867 + ( 1994 + 1 ) × 133
= 1994 × 867 + 1994 × 133 + 133
= 1994 × ( 867 + 133 ) + 133
= 1994 × 1000 + 133
= 1 994 000 + 133
$\text{= 1 994 133}$
$\text{@dautay17747}$
Giải đáp:
Lời giải và giải thích chi tiết:
a , ( 145 xx 99 + 145 ) – ( 143 xx 101 – 143 )
=[145 xx (99 + 1) ] – [143 xx (101- 1)]
=(145 xx 100) – (143 xx100)
=14500 – 14300
=200
_________________________
b , 20 xx 190 xx 50
=( 20 xx50) xx190
=1000 xx 190
=190000
__________________________________
c, 769 x 85 -769 x 75
=769 xx(85 -75)
=769 xx10
=7690
_____________________________________
d , 1994 x 867 + 1995 x 133
=1994 xx (867 + 133)
=1994 xx 1000
=1994000