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1.
a.
11 + x : 5 = 13
x : 5 = 13 - 11
x : 5 = 2
x = 2 . 5
x = 10
Bài 2:
a. $=62-81-12+59-9=(62-12)+(59-9)-81$
$=50+50-81=100-81=19$
b. $=39+13-26-62-39=(39-39)+13-(26+62)$
$=0+13-88=-(88-13)=-75$
c. $=(32-42)+(36-34)+(40-38)=10+2+2=14$
d. $=92-55+8-45=(92+8)-(55+45)=100-100=0$
Bài 1:
a. $=(387-87)-224=300-224=76$
b. $=-(75+35)+379=-110+379=379-110=269$
c. $=(11+15)-(13+17)=25-30=-5$
d. $=(31-21)-(27-24)=10-3=7$
a) (2+4+6+.....+100) . (36.333-108.111)
= (2+4+6+...+100).(36.111.3-108.111)
= (2+4+6+...+100).(108.111-108.111)
= (2+4+6+...+100).0
=0
b) 19991999.1998-19981998.1999
= 1999.10001.1998-1998.10001.1999
= 0
a) ( 2 + 4 + 6 + ... + 100 ) . ( 36.333 - 108.111 )
= ( 2 + 4 + 6 + ... + 100 ) . ( 36.3.111 - 108.111)
= ( 2 + 4 + 6 + ... + 100 ) . ( 108.111 - 108.111 )
= ( 2 + 4 + 6 +... + 100 ) . 0
= 0
b) 19991999.1998 - 19981998 . 1999
= 1999.10001.1998 - 1998.10001 . 1999
= 0
Đáp án cần chọn là: A
(2+4+6+...+100)(36.333−108.111)
=(2+4+6+...+100)(36.3.111−36.3.111)
=(2+4+6+...+100).0=0
a) \(\text{13 x 58 x 4 + 32 x 26 x 2 + 52 x 10 }\)
\(\text{=(13 x 4 ) x 58 + 32 x 13 x 2 x 2 + 13 x 4 x 10}\)
\(\text{= ( 13 x 4 ) x 58 + 32 x ( 13 x 2 x 2 ) + ( 13 x 4 ) x 10 }\)
\(\text{= 52 x 58 + 32 x 52 + 52 x 10}\)
\(\text{=52 x ( 58 + 32 + 10 )}\)
\(\text{=52 x 100 = 5200}\)
b) \(\text{14 x 35 x 5 + 10 x 25 x 7 + 20 x 70 x 2}\)
\(\text{= ( 14 x 5 ) x 35 + (10 x 7 ) x 25 + 20 x 70 x 2 }\)
\(\text{= 70 x 35 + 70 x 25 + 20 x 2 x 70 }\)
\(\text{= 70 x ( 35 + 25 + 40 )}\)
\(\text{= 70 x 100 = 7000 }\)
e) \(\text{5.3.37.4+5.24.21+21.5.12}\)
\(\text{= 5.(3.37.4+24.21+21.12)}\)
\(\text{= 5.1200}\)
\(=6000\)
a, \(120\cdot15+12\cdot470+12\cdot38\cdot10\)
\(=12\cdot10\cdot15+12\cdot47\cdot10+12\cdot38\cdot10\)
\(=120\left(15+47+38\right)=120\cdot100=12000\)
f,\(\left(2+4+6+...+100\right)\cdot\left(36\cdot333-111\cdot108\right)\)
\(=\left(2+4+6+...+100\right)\cdot\left(36\cdot111\cdot3-111\cdot108\right)\)
\(=\left(2+4+6+...+100\right)\cdot111\cdot\left(36\cdot3-108\right)\)
\(=\left(2+4+6+...+100\right)\cdot111\cdot\left(108-108\right)\)
\(=\left(2+4+6+...+100\right)\cdot111\cdot0=0\)
a)
120.15+12.470+12.38.10
=120.15+120.47+120.38=120(15+47+38)=120.100=12000
b)
13.58.4+32.26.2+52.10
=52.58+52.26+52.10=52.(58+26+10)=52.100=5200
c)
3,2.990+32=32.99+32=32.(99+1)=32.100=3200
d)
45.(13+78)+9.(87+22).5
=45.91+45.109=45.(91+109)=45.200=9000
e)
(24+72+36+60):12=12.(2+6+3+5):12=16
f)(2+4+6+...+100)(36.333−108.111)
=(2+4+6+...+100)(36.3.111−36.3.111)=(2+4+6+...+100).0=0