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1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)
\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)
=0
2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)
\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)
\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)
3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)
\(=\dfrac{52546}{15}\)
4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)
\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)
\(=\dfrac{4}{7}\)
\(\dfrac{7}{8}\) \(\times\) \(\dfrac{1}{6}\) + \(\dfrac{7}{8}\) \(\times\) \(\dfrac{2}{6}\) + \(\dfrac{7}{8}\) \(\times\) \(\dfrac{1}{2}\)
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{1}{6}\) + \(\dfrac{2}{6}\) + \(\dfrac{1}{2}\) )
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{3}{6}\) + \(\dfrac{1}{2}\))
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\))
= \(\dfrac{7}{8}\) \(\times\) 1
= \(\dfrac{7}{8}\)
25 \(\times\) 5 \(\times\) 4 \(\times\)2 - 176
= (25 \(\times\) 4 ) \(\times\) ( 5 \(\times\) 2) - 176
= 100 \(\times\) 10 - 176
= 1000 - 176
= 824
\(\dfrac{7}{8}\times\dfrac{1}{6}+\dfrac{7}{8}\times\dfrac{2}{6}+\dfrac{7}{8}\times\dfrac{1}{2}\)
\(=\dfrac{7}{8}\times\left(\dfrac{1}{6}+\dfrac{2}{6}+\dfrac{1}{2}\right)\)
\(=\dfrac{7}{8}\times1\)
\(=\dfrac{7}{8}\)
__________________________
\(25\times5\times4\times2-176\)
\(=\left(25\times4\right)\times\left(4\times2\right)-176\)
\(=1000-176\)
\(=824\)
Chúc bạn học tốt
a, 2x9x5x7x4x25
=2x5x4x25x9x7
=10x100x63
=63000
b,6x14x5x25x3x4
=6x5x3x4x25x14
=90x100x14
=9000x14
=126000
~HT~
a,Cách 1: (6/11 + 5/11 ) x 3/7 Cách 2 :(6/11 + 5/11) x 3/7
= 1 x 3/7 =6/11 x 3/7 + 5/11 x 3/7
= 3/7 = 18/77 + 15/77
= 3/7
b, Cách 1:3/5 x 7/9 - 3/5 x 2/9 Cách 2 :3/5 x 7/9 - 3/5 x 2/9
= 7/15 - 2/15 = 3/5 x (7/9 - 2/9 )
= 1/3 = 3/5 x 5/9
= 1/3
c, Cách 1:(6/7 - 4/7) : 2/5 Cách 2: ( 6/7- 4/7 ) : 2/5
= 2/7 : 2/5 = 6/7 : 2/5 - 4/7 : 2/5
= 5/7 = 15/7 - 10/7
= 5/7
d,Cách 1:8/15 : 2/11 + 7/15 : 2/11 Cách 2:8/15 : 2/11 +7/15 : 2/11
= 88/30 + 77/30 =(8/15+7/15) :2/11
= 11/2 = 1 : 2/11
= 11/2
Bài 2 cậu tự làm nhé !
\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)
\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)
\(=60\times\frac{51}{60}\)
\(=51\)
\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)
\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
Hướng dẫn giải:
a) 71 x 5 x 4 = 71 x (5 x 4) = 71 x 20 = 1420
b) 123 x 50 x 2 = 123 x (50 x 2) = 123 x 100 = 12300
c) 4 x 138 x 25 = (4 x 25) x 138 = 100 x 138 = 13800
d) 25 x 96 x 4 = (25 x 4) x 96 = 100 x 96 = 9600
e) 5 x 81 x 2 = (5 x 2) x 81 = 10 x 81 = 810
g) 50 x 104 x 2 = (50 x 2) x 104 = 100 x 104 = 10400
a, 2.9.5.7.4.25=(2.5).(25.4).(7.9)
=10.100.63=63000
câu b làm tương tự tích giúp mình nha
a)1440:40 =36
b)205 x 13 =2665
c)2057
d)36 x 25 x 4 =3600
18 x 24 :9 =48
41 x 2 x 8 x 5 =3280
215 x 86 + 215 x 14 =21500
53 x 128 - 43 x 128 =1408
2/3 x 4/7 =8/21
2 x 3 x 4 / 2 x 3 x 4 x 5 =24/120
1 x 2 x 3 x 4 / 5 x 6 x 7 x 8=24/1680
x : 7/11 = 22
x =22 x 7/11
x =14
2/7 * x =2/3
x = 2/7 :2/3
x = 20/21
1 : Tính nhanh:
a) 2376 + 3425 - 376 - 425 = ( 2376 - 376 ) + ( 3425 - 425 )
= 2000 + 3000
= 5000
b)4638 - 2437 + 5362 - 7563 = 2210 + ( - 2210 )
= 0
c) 45 + 45 + 45 + 45 + 15 + 15 + 15 + 15
= 45 x 4 + 15 x 4
= ( 45 + 15 ) x 4
= 60 x 4
= 240
d) 4 x 125 x 25 x 8 = ( 4 x 25 ) x ( 125 x 8 )
= 100 x 1000
= 100000
e) 2 x 8 x 50 x 25 x 125 = ( 2 x 50 ) x ( 8 x 125 ) x 25
= 100 x 1000 x 25
= 100000 x 25
= 2500000
2 : Tính nhanh bằng 2 cách:
C1 : 125 + 125 + 125 + 125 - 25 - 25 - 25 - 25
= ( 125 - 25 ) + ( 125 - 25) + ( 125 - 25 ) + ( 125 - 25 )
=100 + 100 + 100 + 100
= 100 x 4
= 400
C2 : 125 + 125 + 125 + 125 - 25 - 25 - 25 - 25
= 125 x 4 - 25 x 4
= ( 125 - 25 ) x 4
= 100 x 4
= 400
a) 4x7x5
=(4x5)x7
=20x7
=140
b) 15x9x2
=(15x2)x9
=30x9
=270
c) 25x895x4
=(25x4)x895
=100x895
=89500
d) 2x3238x50
=(2x50)x3238
=100x3238
=323800
tk nhé
ui avatra idol tui