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\(\left(1-\frac{1}{3}\right).\left(1-\frac{1}{6}\right).\left(1-\frac{1}{10}\right).\left(1-\frac{1}{15}\right)...\left(1-\frac{1}{780}\right).a=1\)
=> \(\frac{2}{3}.\frac{5}{6}.\frac{9}{10}.\frac{14}{15}...\frac{779}{780}.a=1\)
=> \(\frac{4}{6}.\frac{10}{12}.\frac{18}{20}.\frac{28}{30}...\frac{1558}{1560}.a=1\)
=> \(\frac{1.4}{2.3}.\frac{2.5}{3.4}.\frac{3.6}{4.5}.\frac{4.7}{5.6}...\frac{38.41}{39.40}.a=1\)
=> \(\frac{1.2.3.4...38}{2.3.4.5...39}.\frac{4.5.6.7...41}{3.4.5.6...40}.a=1\)
=> \(\frac{1}{39}.\frac{41}{3}.a=1\)
=> \(\frac{41}{117}.a=1\)
=> \(a=1:\frac{41}{117}=\frac{117}{41}\)

X x 9.6 + X x 40% = 2.18
X x (9.6+40%) = 2.18
X x 10 = 2.18
X = 2.18 : 10
X = 0.218

a,
`X-14,5=4,5xx6`
`X-14,5 = 27`
`X = 27 + 14,5`
`X = 41,5`
Vậy ` X = 41,5 `
b,
`X-4,32=25xx4`
`X-4,32= 100`
`X = 100 + 4,32 `
`X = 104,32 `
Vậy ` X = 104,32`

a) \(\dfrac{3}{5}+x=\dfrac{1}{2}+1\)
\(\dfrac{3}{5}+x=\dfrac{3}{2}\)
\(x=\dfrac{3}{2}-\dfrac{3}{5}\)
\(x=\dfrac{15}{10}-\dfrac{6}{10}\)
\(x=\dfrac{9}{10}\)
b) \(3:x=\dfrac{2}{3}+2\dfrac{1}{2}\)
\(3:x=\dfrac{2}{3}+\dfrac{5}{2}\)
\(3:x=\dfrac{4}{6}+\dfrac{15}{6}\)
\(3:x=\dfrac{19}{6}\)
\(x=3:\dfrac{19}{6}\)
\(x=3\times\dfrac{6}{19}\)
\(x=\dfrac{18}{19}\)
Mik nhớ câu này làm rồi mak!!!
a,\(\dfrac{3}{5}\)+ x=\(\dfrac{1}{2}\)+1
\(\dfrac{3}{5}\)+x=\(\dfrac{3}{2}\)
x=\(\dfrac{3}{2}\)-\(\dfrac{3}{5}\)
x=\(\dfrac{9}{10}\)
b,
b) 3:x=23+2123:x=23+212
3:x=23+523:x=23+52
3:x=46+1563:x=46+156
3:x=1963:x=196
x=3:196x=3:196
x=3×619x=3×619
x=1819

a+20%×a=72
ax1+20/100×a=72
a×1+1/5×a=72
a×(1+1/5)=72
a×6/5=72
a=72 : 6/5
a=72×5/6
a=60
Tìm a,biết a+20%xa=72
a+20%xa=72
Ta có: a x 1 + 0,2 x a = 72
a x ( 1 + 0.2 ) = 72
a x 1.2 = 72
a = 72 : 1,2
a = 60
Vậy a bằng 60 !

a) 14,29 - x = 88,24 : 8
14,29 - x = 11,03
x = 14,29 - 11,03
x = 3,26
b) x : 2,4 = 3,8 + 0,45
x : 2,4 = 4,25
x = 4,25 x 2,4
x = 10,2


a: x=2/5*15=6
b: =>x-7=15
=>x=22
c: =>3/4:x+1/2*4=4
=>3/4:x=4-2=2
=>x=3/8

Tổng hai vận tốc : 48 + 54 = 102 ( km/ giờ)
Quãng đường AB là : 2 x 102 = 204 ( km )