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NT
3
KC
15 tháng 7 2018
Tìm x
a) 17 + 33 : ( 2 . x - 1 ) = 20
33 :( 2 . x - 1 )= 20 - 17
33 :( 2 . x - 1 ) = 3
2 . x - 1 = 33 : 3
2 . x - 1 = 11
2 . x = 11 - 1 = 10
x = 10 : 2
x = 5
b) 25 - [ ( 2 . x + 5 ) . 7 - 15 ] : 5 = 21
[ ( 2 . x + 5 ) . 7 - 15 ] : 5 = 25 - 21
[ ( 2 . x + 5 ) . 7 - 15 ] : 5 = 4
( 2 . x + 5 ) . 7 - 15 = 5 x 4
( 2 . x + 5 ) . 7 - 15 = 20
( 2 . x + 5 ) . 7 = 20 + 15
( 2 . x + 5 ) . 7 = 35
2 . x + 5 = 35 : 7
2 . x + 5 = 5
2 . x = 5 - 5
2 . x = 0
x = 0
hok tốt
15 tháng 7 2018
a) \(17+33:\left(2x-1\right)=20\)
\(\Rightarrow33:\left(2x-1\right)=20-17\)
\(\Rightarrow33:\left(2x-1\right)=3\)
\(\Rightarrow2x-1=33:3\)
\(\Rightarrow2x-1=11\)
\(\Rightarrow2x=11+1\)
\(\Rightarrow2x=12\)
\(\Rightarrow x=12:2\)
\(\Rightarrow x=6\)
Vậy x = 6
b) \(25-\left[\left(2x+5\right)\times7-15\right]:5=21\)
\(\Rightarrow\left[\left(2x+5\right)\times7-15\right]:5=25-21\)
\(\Rightarrow\left[\left(2x+5\right)\times7-15\right]:5=4\)
\(\Rightarrow\left(2x+5\right)\times7-15=4\times5\)
\(\Rightarrow\left(2x+5\right)\times7-15=20\)
\(\Rightarrow\left(2x+5\right)\times7=20+15\)
\(\Rightarrow\left(2x+5\right)\times7=35\)
\(\Rightarrow2x+5=35:7\)
\(\Rightarrow2x+5=5\)
\(\Rightarrow2x=5-5\)
\(\Rightarrow2x=0\)
\(\Rightarrow x=0:2\)
\(\Rightarrow x=0\)
Vậy x = 0
_Chúc bạn học tốt_
24 tháng 7 2023
a)
\(\dfrac{1}{2}=0,5;\dfrac{3}{4}=0,75;\dfrac{7}{5}=1,4;\dfrac{9}{8}=1,125;\dfrac{26}{25}=1,04;\dfrac{120}{125}=0,96\)
b)
\(\dfrac{15}{25}=0,6;\dfrac{75}{25}=3;\dfrac{90}{300}=0,3;\dfrac{27}{36}=0,75;\dfrac{51}{85}=0,6\)
24 tháng 7 2023
a,1/2=5/10;3/4=75/100;7/5=140/100;26/25=108/100;120/125=960/1000
b,15/25=60/100;75/25=300/100;90/300=3/10;27/36=3/4=75/100;
51/85=3/5=60/100;39/65=3/5=60/100
HL
2
15 tháng 9 2021
bỏ tạm 38/25 ra
=(9/10-11/15) +(13/21-15/28) +(197/4851-199/4950)
=1/6+1/12+1/20+...+1/49*50=2450
=3-2/2x3+4-3/3x4+5-4/4x5+....50-49/49x50
=1/2-1/3+1/3-...-1/50
1/2-1/50=12/25
=38/25+12/25=50/25
=2
DT
2
AH
Akai Haruma
Giáo viên
25 tháng 9 2023
Lời giải:
$25\frac{2}{13}-(\frac{15}{17}+15\frac{2}{13)$
$=25+\frac{2}{13}-\frac{15}{17}-15-\frac{2}{13}$
$=(25-15)+(\frac{2}{13}-\frac{2}{13})-\frac{15}{17}$
$=10-\frac{15}{17}=\frac{155}{17}$
7 tháng 7 2023
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) \(\dfrac{12}{7}\div x+\dfrac{2}{3}=\dfrac{7}{5}\)
\(\dfrac{12}{7}\div x=\dfrac{7}{5}-\dfrac{2}{3}\)
\(\dfrac{12}{7}\div x=\dfrac{11}{15}\)
\(x=\dfrac{12}{7}\div\dfrac{11}{15}\)
\(x=\dfrac{180}{77}\)
BP
0
DP
1
a) 17 x 25 + 25 x 33 +25 x 50 = 25 x (17 + 33 + 50)
= 25 x 100 = 2500
b) 125 x 15 -25 x 15 = 15 x (125 - 25)
= 15 x 100 = 1500
a. 17.25+25.33+25.50
= 25.(17+33+50)
= 25.100
= 2500
b. 125.15-25.15
= 15.(125-25)
= 15.100
= 1500