13.17-256:16+14:7-1
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KQ
1
15 tháng 8 2018
a) 27.25 + 25.27 - 150
= 27 ( 25+25 ) - 150
= 27.100 - 150
= 2700 - 150 = 2550
b) 12 : { 400 : [ 500 - ( 125 + 25.7) ] }
= 12: { 400 : ( 500 - 300 ) }
= 12 : ( 400 : 200 )
= 12 : 2
= 6
c) 13.17 - 256 : 16 + 14:7 - 1
= 221 - 16 + 2 - 1
= 206
Chúc bạn hok tốt~
25 tháng 2 2020
a,27.75+25.27-150
=27.(75+25)-150
=27.100-150
=2700-150
=2550
c,13.17-256:16+14:7-1
=221-16+2-1
=205+2-1
=208-1
=207
d,18:3+182+3.(51:17)
=18:3+182+3.3
=6+182+9
=188+9
=197
e,15-25:8(100.2)
=15-25:8.200
=15-3,125.200
=15-625
=-610
f,25.8-12.5+170:17-8
=200-60+10-8
=140+10-8
=150-8
=142
H9
HT.Phong (9A5)
CTVHS
13 tháng 7 2023
a) \(227+50+23=\left(227+23\right)+50=250+50=300\)
b) \(135+360+65+40=\left(135+65\right)+\left(360+40\right)=200+400=600\)
c) \(1+2+3+4+5+...+97+98+99+100\)
\(=\left(100+1\right)+\left(99+2\right)+...+\left(50+51\right)\)
\(=101+101+101+...+101\)
\(=101\cdot50\)
\(\Leftrightarrow5050\)
d) \(115\cdot13-13\cdot15=13\cdot\left(115-15\right)=13\cdot100=1300\)
e) \(50-49+48-47+...+4-3+2-1\)
\(=\left(50-49\right)+\left(48-47\right)+...+\left(2-1\right)\)
\(=1+1+1+1+..+1\)
\(=1\cdot25\)
\(=25\)
H9
HT.Phong (9A5)
CTVHS
13 tháng 7 2023
f) \(30\cdot40\cdot50\cdot60=10\cdot3+10\cdot4+10\cdot5+10\cdot6\)
\(=10\cdot10\cdot10\cdot10\cdot3\cdot4\cdot5\cdot6\)
\(=10000\cdot360\)
\(=3600000\)
g) \(27\cdot36+27\cdot64=27\cdot\left(36+64\right)=27\cdot100=2700\)
h) \(5\cdot2^2-18:3=5\cdot4-18:3=20-6=14\)
i) \(13\cdot17-256:16+14:7-2021^0\)
\(=13\cdot17-4^4:4^2+2-1\)
\(=13\cdot17-16+2-1\)
\(=13\cdot17-17\)
\(=17\cdot\left(13-1\right)\)
\(=204\)
j) \(7^2-36:3=49-12=37\)
HT
4
YN
23 tháng 7 2020
13 x 17 - 256 : 16 + 14 : 7 - 1
= 221 - 16 + 2 - 1
= 205 + 2 - 1
= 207 - 1
=206
23 tháng 7 2020
13 . 17 - 256 : 16 + 14 : 7 - 1 = 221 - 16 + 2 - 1 = 205 -2 -1 = 203 - 1= 202
H9
HT.Phong (9A5)
CTVHS
22 tháng 7 2023
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) \(38\cdot x-12\cdot x-x\cdot16=40\)
\(\Rightarrow x\cdot\left(38-12-16\right)=40\)
\(\Rightarrow x\cdot10=40\)
\(\Rightarrow x=40:10\)
\(\Rightarrow x=4\)
21 tháng 2 2021
1: Ta có: \(2155-\left(174+2155\right)+\left(-68+174\right)\)
\(=2155-174-2155-68+174\)
=-68
2) Ta có: \(-25\cdot72+25\cdot21-49\cdot25\)
\(=-25\cdot\left(72-21+49\right)\)
\(=-25\cdot100=-2500\)
ND
1
TA
12 tháng 6 2023
\(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+...+\dfrac{1}{x}=\dfrac{127}{256}\)
Đặt VT là A
\(\Rightarrow2A=1+\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{2}{x}\)
\(2A-A=\left(1+\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{2}{x}\right)-\left(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+...+\dfrac{1}{x}\right)=\dfrac{127}{256}\)
\(\Leftrightarrow A=1-\dfrac{1}{x}=\dfrac{127}{256}\)
\(\Leftrightarrow\dfrac{1}{x}=\dfrac{129}{256}\)
\(\Rightarrow x=\dfrac{256}{129}\)
=221-16+2-1
=205+1
=206
vậy nhó
=221-16+2-1=206