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18 * 23 +3 +45 * 6 +9 * 32 *2 =1263
425 *7*4 - 170 *60=1700
132 *9 +132 =1320
( 56* 27 +56 +35 ):62=\(\frac{1603}{62}\)
39 * ( 250 +87) +61 * ( 240 +97)=33700
Hk tốt!!! k cho mình nha!!@@
35 . 23 .+ 35 . 41 + 64 . 65 =35(23+41)+64.65=35.64+64.65=64(35+65)=64.100=6400
29 . 87 - 29 . 23 + 64 . 71 =29(87-23)+64.71=29.64+64.71=64(29+71)=29.100=2900
27 . 121 - 87 . 27 + 73 . 34 =27(121-87)+73.34=27.34+73.34=34(27+73)=34.100=3400
35 . 23 + 35 . 41 + 64 . 65 29 . 87 - 29 . 23 + 64 . 71
= 35 . ( 23 + 41 ) + 64 . 65 = 29 . ( 87 - 23 ) + 64 . 71
= 35 . 64 + 64 . 65 = 29 . 64 + 64 . 71
= 64 . ( 35 + 65 ) = 64 . ( 29 + 71 )
= 64 . 100 = 64 . 100
= 6400 = 6400
27 . 121 - 87 . 27 + 73 . 34
= 27 . ( 121 - 87 ) + 73 . 34
= 27 . 34 + 73 . 34
= 34 . ( 27 + 73 )
= 34 . 100
= 3400
Đó chính là câu trả lời bạn nhớ tích cho mình nhé
a) 35.23+35.41+64.65
= 35.(23+41)+64.65
=35.64+64.65
=64.(35+65)
=64.100
=6400
b) 29.87-29.23+64.71
=29.(87-23)+64.71
=29.64+64.71
=64.(29+71)
=64.100
=6400
c) 27.121-87.27+73.34
=27.(121-87)+73.34
=27.34+73.34
=34.(27+73)
=34.100
=3400
x.20+60=160+500
x.20+60=660
x.20=660-60
x.20=600
x=600:20
x=30
35.56+35.44
=35.(56+44)
=35.100
=3500
\(I=\frac{5}{6}+\frac{5}{12}+\frac{5}{20}+...+\frac{5}{90}\)( viết tắt )
\(I=\frac{5}{2.3}+\frac{5}{3.4}+\frac{5}{4.5}+...+\frac{5}{9.10}\)
\(I=5\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)
\(I=5\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(I=5\left(\frac{1}{2}-\frac{1}{10}\right)\)
\(I=5\times\frac{2}{5}\)
\(I=2\)
Vậy \(I=2\)
Tk nha bn ~~
\(I=\frac{5}{6}+\frac{5}{12}+\frac{5}{20}+\frac{5}{30}+\frac{5}{42}+\frac{5}{56}+\frac{5}{72}+\frac{5}{90}\)
\(I=\frac{5}{2\cdot3}+\frac{5}{3\cdot4}+\frac{5}{4\cdot5}+\frac{5}{5\cdot6}+\frac{5}{6\cdot7}+\frac{5}{7\cdot8}+\frac{5}{8\cdot9}+\frac{5}{9\cdot10}\)
\(I=5\left(\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}+\frac{1}{9\cdot10}\right)\)
Theo tính chất của toán HSG lớp 6, ta được
\(I=5\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)
\(I=5\left(\frac{1}{2}-\frac{1}{10}\right)\)
\(I=5\left(\frac{5}{10}-\frac{1}{10}\right)\)
\(I=5\cdot\frac{4}{10}=5\cdot\frac{2}{5}=\frac{10}{5}=2\)
a) \(74\frac{19}{35}.\frac{7}{90}+15\frac{16}{35}.\frac{7}{90}+2\frac{14}{90}\)
= \(\left(74\frac{19}{35}+15\frac{16}{35}\right).\frac{7}{90}+2\frac{14}{90}\)
= 90 . 7/90 + 194/90
= 630/90 + 194/90
= 824/90 = 412/45
b) (-2/5 + 3/7) - (4/9 + 12/20 - 13/35) + 7/35
= -2/5 + 3/7 - 4/9 - 3/5 + 13/35 + 7/35
= (-2/5 - 3/5) + 3/7 - 4/9 + (13/35 + 7/35)
= -1 + 3/7 - 4/9 + 4/7
= -1 + (3/7 + 4/7) - 4/9
= -1 + 1 - 4/9 = -4/9
a) 13 + 87 : 100
= (13 + 87) : 100
= 100 : 100
= 1
b) 30 + 12 + 70 + 88
= (30 + 70) + (12 + 88)
= 100 + 100
= 200
c) 55 + 44 + 45
= (55 + 45) + 44
= 100 + 44
= 144
c) 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10
= (1 + 9) + (2 + 8) + (3 + 7) + (4 + 6) + 5
= 10 + 10 + 10 + 10 + 5
= 40 + 5
= 45
a ) 1
b ) 30 + 12 + 70 + 88
= ( 30 + 70 ) + ( 88 + 13 )
= 100 + 100
= 200
c ) 55 + 44 + 45
= ( 55 + 45 ) + 44
= 100 + 44
= 144
d ) 1+2+3+4+5+6+7+8+9
= ( 1+9 ) + ( 2+8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5
= 10 + 10 + 10 + 10 + 5
= 45
nhieu qua