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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: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)
\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)
\(=\dfrac{4}{7}\)
35 x 20 x 5 8 x 9 x 125 25 x 7 x 4 72:(8x3)
= 35 x ( 20 x5 ) = ( 8x125) x 9 = (25x4)x7 = 72: 24
= 35 x 100 = 1 000 x 9 = 100x7 = 3
= 3 500 = 9 000 =700
(36x7):4
=36: 4 x 7
= 9 x7
= 63
35 x 20 x 5 = 35\(\times\)(20 \(\times\)5)= 35 \(\times\)100=3500
8 \(\times\)9 \(\times\) 125 =(8\(\times\) 125)\(\times\)9=1000\(\times\)9=9000
25 \(\times\)7\(\times\)4=(25 \(\times\)4)\(\times\)7=100\(\times\)7=700
72 : (8\(\times\)3)=72 : 8 x 3 =(72:8) x 3=9 x 3=27
(36 x 7) : 4 =36 x 7 : 4 =7 x (36 :4)=7 x 9=63
1. A) 225886 + 779 × 8
= 225886 + 6232
= 232118
B) 125 × 5 × 20 × 8
= (125 × 8) × (5 × 20)
= 1000 × 100
= 100000
C) 47286 : 2 + 14765
= 23643 + 14765
= 38408
D) 91428 - 23560 : 5
= 91428 - 4712
= 86716
3. A) 36 × 532 + 63 × 532 + 532
= 532 × (36 + 63 + 1)
= 532 × 100
= 53200
B) 679 × 123 + 679 - 679 × 24
= 679 × (123 + 1 - 24)
= 679 × 100
= 67900
C) 245 × 327 - 245 × 18 - 9 × 245
= 246 × (327 - 18 - 9)
= 245 × 300
= 73500
2 x 175 x 5
= ( 2 x 5 ) x 175
= 10 x 175
= 1750
263 x 15 x 4
= 263 x ( 15 x 4 )
= 263 x 60
15780
20 x 198 x 4
= ( 20 x 4 ) x 198
= 80 x 198
= 15840
505 x 35 x 2
= 505 x ( 35 x 2 )
= 505 x 70
= 35350
tk nha
2 x 175 x 5
= ( 2 x 5 ) x 175
= 10 x 175
= 1750
20 x 198 x 4
= ( 20 x 4 ) x 198
= 80 x 198
= 15840
còn lại tự làm nha