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1. Q=165+247+528+125+315
= 100+60+5+200+40+7+500+20+8+100+20+5+300+10+5
= ( 100+200+500+100+300) + ( 60+40+20+20+10 ) +( 5+7+8+5+5 )
= 1200+150+30
=1280
R=1234+5678+8+80
=1000+200+30+4+5000+600+70+8+8+80
= ( 1000+5000) + ( 200+600 ) + (30+70+80) + ( 4+8+8)
=6000+800+180+20
=7000
Bài 1
Tính : Q=165+247+528+125+315
=(165+125)+(247+315+528)
=290+1090
= 1380
R=1234+5678+8+80
=(1234+6)+(5678+2)+80
= 1240+5680+80
= (1240+60)+(5680+20)
=1300+5700=7000
Bài 2:
A= 243-97=(243+7)-(97-7)=250-90=160
B= 400-42-58=400-(42+58)=400-100=300
C=600-67-33=600-(67+33)=600-100=500
D=200-24-46=200-(24+46)=200-70=130
E=400-5-6-7-8=400-(5+6+7+8)=400-26=374
F= 764-115-268-43-32-20-85-37
=764-(115+85)-(268+32)-(43+37)-20
=764-200-300-80-20
=164
G=350-7-18-52-48-72
=350-(18+72)-(52+48)-7
=350-90-100-7
=160-7
=153
\(Q=165+247+528+125+315\)
\(=\left(247+528+125\right)+\left(165+315\right)\)
\(=900+480\)
\(=1280\)
\(R=1000+200+30+4+5000+600+70+8+80\)
\(=\left(1000+5000\right)+\left(200+600\right)+\left(30+70+80\right)+\left(4+8+8\right)\)
\(=6000+800+180+20\)
\(=6000+\left(800+100\right)+\left(80+20\right)\)
\(=6000+900+100\)
\(=7000\)
a ) 2 15 b ) − 2 5 c ) 1 d ) 1 e ) − 5 3 f ) 0 g ) 2 3 5 h ) 1
d) Ta có: \(-8+\left(-14\right)+34+\left(-12\right)\)
\(=-8-14+34-12\)
\(=-20+20\)
\(=-0\)
e) Ta có: \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)
\(=\left(-7+57\right)+\left(-20-30\right)\)
\(=50-50=0\)
f) Ta có: \(300-\left(-180\right)-120-42\)
\(=300+180-120-42\)
\(=258+60=318\)
d, Ta có : \(\left(-8\right)+\left(-14\right)+34+\left(-12\right)\)
\(=-\left(8+12\right)+34-14=-20+20=0\)
e, Ta có : \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)
\(=-\left(30+20\right)+57-7=-50+50=0\)
f, Ta có : \(300-\left(-180\right)-120-42=318\)
\(\left(\frac{-1}{4}+\frac{7}{33}-\frac{5}{3}\right)-\left(\frac{-5}{4}+\frac{6}{11}-\frac{48}{49}\right)=\left(\frac{-1}{4}-\frac{16}{11}\right)-\left(-\frac{31}{44}-\frac{48}{49}\right)=-\frac{1}{4}-\frac{16}{11}+\frac{31}{44}+\frac{48}{49}=-\frac{1}{49}\)
Bài 2:
a: =>x-35=-23
=>x=12
b: =>|x-8|=13
=>x-8=13 hoặc x-8=-13
=>x=21 hoặc x=-5
Bài 1:
a: =42-98-42+12-12=-98
b: =10x4x3x(-25)=40x(-25)x3=-1000x3=-3000
a) 27.97-27.17+80.73
=27.(97-17)+80.73
=27.80+80.73
=80.(27+73)
=80.100
=8000
b) (-33)+36+(-39)+42+(-45)+48
=-33+36-39+42-45+48
=9