Tính nhanh giá trị biểu thức:
b) ( 198 : 18 - 144 :13 ) × ( 16996 - 1110 : 30 × 305 )
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Lời giải:
$=(111-\frac{1743}{13})\times (16996-11285)$
$=\frac{-300}{13}\times 5711=\frac{-1713300}{13}$
[1998: 18 - 1443 : 13 ] nhân [16996 - 1110 ; 30 nhân 305 ] = 0
A) \(\frac{131313}{151515}+\frac{131313}{353535}+\frac{131313}{636363}+\frac{131313}{999999}\)
\(=\frac{10101\times13}{10101\times15}+\frac{10101\times13}{10101\times35}+\frac{10101\times13}{10101\times63}+\frac{10101\times13}{10101\times99}\)
\(=\frac{13}{15}+\frac{13}{35}+\frac{13}{63}+\frac{13}{99}\)
\(=13\times\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\)
\(=13\times\frac{4}{33}=\frac{52}{33}\)
B) \(\left(1998:18-1443:13\right)\times\left(16996-1110:30\times305\right)\)
\(=\left(111-111\right)\times\left(16996-1110:30\times305\right)\)
\(=0\times\left(16996-1110:30\times305\right)\)
\(=0\)
( TẤT CẢ MỌI SỐ NHÂN VỚI 0 ĐỀU BẰNG 0)
C) \(\left(\frac{575757}{424242}+\frac{575757}{565656}+\frac{575757}{727272}\right)\times18\)
\(=\left(\frac{10101\times57}{10101\times42}+\frac{10101\times57}{10101\times56}+\frac{10101\times57}{10101\times72}\right)\times8\)
\(=\left(\frac{57}{42}+\frac{57}{56}+\frac{57}{72}\right)\times8\)
\(=\left(\frac{1}{42}+\frac{1}{56}+\frac{1}{72}\right)\times57\times8\)
\(=\frac{1}{169344}\times57\times8\)
\(=\frac{19}{7056}\)
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a, = 13/15 + 13/35 + 13/63 + 13/99
= 13.( 1/15 + 1/35 + 1/63 + 1/99 )
= 13.( 1/ 3.5 + 1/5.7 + 1/7.9 + 1/ 9.11)
= 13 . ( 1/3 - 1/5 +1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11)
= 13 . ( 1/3 - 1/11)
= 13 . 3/11 = 39/11
a.
\(\left(100+42\right)\times42+\left(200-58\right)\times58=142\times42+142\times58=142\times\left(42+58\right)=142\times100=14200\)
b.
\(\left(1998\div18-1443\div13\right)\times\left(16996-1110\div30\times305\right)=\left(111-111\right)\times\left(16996-1110\div30\times305\right)\)
\(=0\times\left(16996-1110\div30\times305\right)=0\)
c.
\(5^3_5+1,75+6^1_8+4^1_4+3,875+3,4=5,6+1,75+6,125+4,25+3,875+3,4\)
\(=\left(5,6+3,4\right)+\left(1,75+4,25\right)+\left(6,125+3,875\right)=9+6+10=25\)
\(A=2016:4+4048:2\\ =504+2024\\ =2528\\ B=37064-64\cdot\left(82+42966:2017\right)\\ =37064-64\cdot\left(82+21,30193356\right)\\ =37064-64\cdot103,3019336\\ =37064-6611,323748\\ =30452,67625\\ C=\left(100+92\cdot42\right)+\left(200-58\right)\cdot58\\ =\left(100+3864\right)+142\cdot58\\ =3964+8236\\ =12200\\ D=\left(1998:18-1443:13\right)\cdot\left(16996-1110:30\cdot305\right)\\ =\left(111-111\right)\cdot\left(16996-1110:30\cdot305\right)\\ =0\cdot\left(16996-1110:30\cdot305\right)\\ =0\)
2,
a) \(315-\left(135-x\right)=215\)
\(\Rightarrow135-x=315-215\)
\(\Rightarrow135-x=100\)
\(\Rightarrow x=135-100\)
\(\Rightarrow x=35\)
b) \(x-320:32=25\cdot16\)
\(\Rightarrow x-10=5^2\cdot4^2\)
\(\Rightarrow x-10=20^2\)
\(\Rightarrow x-10=400\)
\(\Rightarrow x=410\)
c) \(3\cdot x-2018:2=23\)
\(=3\cdot x-1009=23\)
\(\Rightarrow3\cdot x=1032\)
\(\Rightarrow x=1032:3\)
\(\Rightarrow x=344\)
d) \(280-9\cdot x-x=80\)
\(\Rightarrow280-x\cdot\left(9+1\right)=80\)
\(\Rightarrow280-10\cdot x=80\)
\(\Rightarrow10\cdot x=280-80\)
\(\Rightarrow10\cdot x=200\)
\(\Rightarrow x=20\)
e) \(38\cdot x-12\cdot x-x\cdot16=40\)
\(\Rightarrow x\cdot\left(38-12-16\right)=40\)
\(\Rightarrow x\cdot10=40\)
\(\Rightarrow x=40:10\)
\(\Rightarrow x=4\)
( 198 : 18 - 143 : 13 ) x ( 16996 - 1110 : 30 x 305 )
= ( 11 - 11 ) x ( 16996 - 1110 : 30 x 305 )
= 0 x ( 16996 - 1110 : 30 x 305 )
= 0