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\(37\times46+37\times51+111\)
\(=37\times46+37\times51+37\times3\)
\(=37\times\left(46+51+3\right)\)
\(=37\times100\)
\(=3700\)
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\(172\times47+86\times8-34\times4\)
\(=172\times47+172\times4-34\times4\)
\(=172\times\left(47+4\right)-34\times4\)
\(=172\times51-34\times4\)
\(=172\times3\times17-17\times2\times4\)
\(=17\times\left(172\times3-2\times4\right)\)
\(=17\times\left(516-8\right)\)
\(=17\times508\)
\(=8636\)
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\(35\times215-35\times200-175\)
\(=35\times215-35\times200-35\times5\)
\(=35\times\left(215-200-5\right)\)
\(=35\times10\)
\(=350\)
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\(48\times56+28\times104\)
\(=48\times2\times28+28\times104\)
\(=28\times\left(48\times2+104\right)\)
\(=28\times200\)
\(=5600\)
a) \(37\times46+37\times51+111\)
\(=37\times46+37\times51+37\times3\)
\(=37\times\left(46+51+3\right)\)
\(=37\times100\)
\(=3700\)
b) \(35\times215-35\times210-175\)
\(=35\times215-35\times210-35\times5\)
\(=35\times\left(215-210-5\right)\)
\(=35\times0\)
\(=0\)
c) \(172\times47+86\times8-34\times4\)
\(=4\times\left(43\times47+86\times2-34\right)\)
\(=4\times\left(2021+172-34\right)\)
\(=4\times2159\)
\(=8636\)
d) \(48\times56+28\times104\)
\(=48\times56+56\times52\)
\(=56\times\left(48+52\right)\)
\(=56\times100\)
\(=5600\)
a. \(\Leftrightarrow\) (3.x+4):12 = 19-17
\(\Leftrightarrow\)(3.x+4):12 = 2
\(\Leftrightarrow\)3.x+4 = 24 \(\Leftrightarrow\)3.x = 20 \(\Leftrightarrow\)x = \(\frac{20}{3}\)
b. \(\Leftrightarrow\)45: (2.x+1) = 3 \(\Leftrightarrow\)2.x+1 = 15 \(\Leftrightarrow\)2.x = 14 \(\Leftrightarrow\)x = 7
c. \(\Leftrightarrow\)72.(x+1) = 360 \(\Leftrightarrow\)x+1 = 5\(\Leftrightarrow\)x = 4
d.\(\Leftrightarrow\)(2.x+3).11 = 253\(\Leftrightarrow\)2.x+3 = 23\(\Leftrightarrow\)2.x = 20\(\Leftrightarrow\)x = 10
123,45 + 23,56 +76,44 + 54,55
= (123,45 + 54,55) + (23,56 + 76,44)
= 178 + 100
= 278
456 x 45 + 456 x 10 + - 456 x 55
=456 x (45 +10-55)
=456 x 0
=0
2,5 x 8,5 + 7,5 x 8,5
=8,5 x (2,5 +7,5)
= 8,5 x 10
= 85
86 x 5 + 86 x 4 + 86
= 86 x (5+4+1)
= 86 x10
860
Bài 1
a) \(5\times72\times10\times2=\left(5\times2\times10\right)\times72=100\times72=7200\)
b) \(40\times125=5\times\left(8\times125\right)=5\times1000=5000\)
c) \(16\times6\times25=4\times4\times6\times25=\left(4\times6\right)\times\left(4\times25\right)=24\times100=2400\) Bài 2:
a) \(24\times57+43\times24=24\times\left(57+43\right)=24\times100=2400\)
b) \(12\times19+80\times12+12=12\times\left(19+80+1\right)=12\times100=1200\)
c) \(\left(36\times15\times169\right)\div\left(5\times18\times13\right)\)
\(=\left(18\times2\times3\times5\times13\times13\right)\div\left(5\times18\times13\right)\)
\(=\left(2\times3\times13\right)\times\left(18\times5\times13\right)\div\left(5\times18\times13\right)\)
\(=2\times3\times13\)
\(=78\)
d) \(\left(44\times52\times60\right)\div\left(11\times13\times15\right)\)
\(=\left(4\times11\times4\times13\times4\times15\right)\div\left(11\times13\times15\right)\)
\(=\left(4\times4\times4\right)\times\left(11\times13\times15\right)\div\left(11\times13\times15\right)\)
\(=4\times4\times4\)
\(=64\)
Bài 3:
a) \(x-280\div35=5\times54\)
\(x-8=270\)
\(x=270+8\)
\(x=278\)
b) \(\left(x-280\right)\div35=54\div4\)
\(\left(x-280\right)\div35=\dfrac{27}{2}\)
\(x-280=\dfrac{27}{2}\times35\)
\(x-280=\dfrac{945}{2}\)
\(x=\dfrac{945}{2}+280\)
\(x=\dfrac{1505}{2}\)
c) \(\left(x-128+20\right)\div192=0\)
\(x-128+20=0\times192\)
\(x-128+20=0\)
\(x-128=0-20\)
\(x-128=-20\)
\(x=-20+128\)
\(x=108\)
d) \(4\times\left(x+200\right)=460+85\times4\)
\(4\times\left(x+200\right)=460+340\)
\(4\times\left(x+200\right)=800\)
\(x+200=800\div4\)
\(x+200=200\)
\(x=200-200\)
\(x=0\)
Bài 4:
a) \(\dfrac{7}{12}-\dfrac{5}{12}=\dfrac{2}{12}=\dfrac{1}{6}\)
b) \(\dfrac{8}{11}+\dfrac{19}{11}=\dfrac{27}{11}\)
c) \(\dfrac{3}{8}+\dfrac{5}{12}=\dfrac{9}{24}+\dfrac{10}{24}=\dfrac{19}{24}\)
d) \(\dfrac{3}{4}+\dfrac{7}{12}=\dfrac{9}{12}+\dfrac{7}{12}=\dfrac{16}{12}=\dfrac{4}{3}\)
Bài 5:
a) \(x-\dfrac{6}{7}=\dfrac{5}{2}\)
\(x=\dfrac{5}{2}+\dfrac{6}{7}\)
\(x=\dfrac{47}{14}\)
b) \(\dfrac{12}{7}\div x+\dfrac{2}{3}=\dfrac{7}{5}\)
\(\dfrac{12}{7}\div x=\dfrac{7}{5}-\dfrac{2}{3}\)
\(\dfrac{12}{7}\div x=\dfrac{11}{15}\)
\(x=\dfrac{12}{7}\div\dfrac{11}{15}\)
\(x=\dfrac{180}{77}\)
a) 6625 + 3525 - 25 d) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45
= 6625 + ( 3525 -25) = 35 x (34 + 86 ) + 65 x (75 + 45 )
= 6625 + 3500 = 35 x 120 + 65 x 120
= 10 125 = 120 x ( 35 + 65 )
= 120 x 100
= 12 000
a) 6625 + 3525 - 25
=10125
b) 58 x 42 + 32 x 8 + 5 x 16
= 2436 + 256 + 80
= 2772
c) (4243 + 4357 + 43) - 360 : 4
= 8643 - 360: 4
= 8642 - 90
= 8552
d) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45
= (34 +86) x 35 + (75 + 45) x 65
= 120 x 35 + 120 x 65
= 120 x (35+65)
= 120 x 100
= 12000
Dãy số có 2 chữ số chia hết cho 3 là:[12,15,....,99]
Khoảng cách của từng số hạng là 3
Số số hạng là: (99-12):3+1=30(số)
Vậy có 30 số có 2 chữ số chia hết cho 3
Tính nhanh
Gọi A , B , C , D là 4 biểu thức đầu tiên
A x B x C x D x ( 45 x 128 - 90 x 64 )
= A x B x C x D x ( 45 x 128 - 45 x 2 x 64 )
= A x B x C x D x ( 45 x 128 - 45 x 128 )
= A x B x C x D x 0
= 0
Vậy kết quả của biểu thức là 0
Gọi A , B , C , D là 4 biểu thức đầu tiên
A x B x C x D x ( 45 x 128 - 90 x 64 )
= A x B x C x D x ( 45 x 128 - 45 x 2 x 64 )
= A x B x C x D x ( 45 x 128 - 45 x 128 )
= A x B x C x D x 0
= 0
Vậy kết quả của biểu thức là 0
a) 19 x 41 + 57 x 16 + 19
= 19 x 41 + 19 x 3 x 16 + 19
= 19 x ( 41 + 3 x 16 + 1 )
= 19 x 90 = 1710
b) 45 x 215 - 45 x 210 - 45 x 5
= 45 x ( 215-210-5 )
= 45 x 0 = 0
c) 86 x 94 + 86 x 2 + 172 x 2
= 86 x 94 + 86 x 2 + 86 x 4
= 86 x ( 94 + 2 + 4 )
= 86 x 100 = 8600
d) 48 x 72 + 36 x 104
= 48 x 72 + 72 x 52
= 72 x ( 48 + 52 )
= 72 x 100
= 7200