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Bài 1:
a: \(=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{12}+\dfrac{1}{12}-\dfrac{1}{17}\)
=1/3-1/17
=4/51
b: \(=\left(2+3+4+...+23\right)+0.3\cdot22\)
=(23+2)*(23-2+1)/2+6,6
=275+6,6
=281,6
Câu đầu:
12/5 - X x 3/4 =5/4
X x 3/4 =12/5 - 5/4 ra X x 3/4 = 23/20 , X = 23/20 : 3/4 ,X=23/15
Câu hai:
X : 3/5 + 3/8 =15/8
X : 3/5 =15/8 - 3/8 ra X : 3/5 = 15/8 , X= 15/8 x 3/5,X= 9/8
\(\frac{15}{8}\)+\(\frac{7}{12}\)-\(\frac{13}{3}\)x\(\frac{3}{8}\)
=\(\frac{45}{24}\)+\(\frac{14}{24}\)-\(\frac{13}{8}\)
=\(\frac{59}{24}\)-\(\frac{39}{24}\)
=\(\frac{20}{24}\)=\(\frac{5}{6}\)
\(\frac{11}{5}\)+\(\frac{5}{22}\):2+\(\frac{5}{6}\)
=\(\frac{11}{5}\)+\(\frac{5}{44}\)+\(\frac{5}{6}\)
=\(\frac{484}{220}\)+\(\frac{25}{220}\)+\(\frac{5}{6}\)
=\(\frac{509}{220}\)+\(\frac{5}{6}\)
=\(\frac{1527}{660}\)+\(\frac{550}{660}\)
=\(\frac{2077}{660}\)
`\text {12 ngày 8 giờ - 2 ngày 15 giờ x 3 = 12 ngày 8 giờ - 7 ngày 21 giờ = 4 ngày 11 giờ}`
`11/12 \times 5/6 \times 4/3=55/72 \times 43=55/54`
`5/7+3/8 \div 9/2=5/7+1/12=67/84`
A) 1000000 - 107492 : 154 x 28 + 1000
= 1000000 - 19544 + 1000
= 981456
B) 8/15 + 4/7 + 14/30 + 12/21 + 5
= 15/7 + 5
= 50/7
C) 9/13 : 6/11 - 5/12 : 6/11
= 9/13 x 11/6 - 5/12 x 11/6
= (9/13 - 5/12) x 11/6
= 43/156 x 11/6
= 473/936
Bài 2
1) X x2 + X x 1/5 = 8/5
X x (2 + 1/5 ) = 8/5
X x 11/5 = 8/5
X = 8/5 x 5/11
X = 8/11
2) X : 3/8 = 4/3 : 3/6
X : 3/8 = 8/3
X = 8/3 x 3/8
X = 1
a) 1 000 000 - 107 492 : 154 x 28 + 1000
= 1 000 000 - 698 x 28 + 1000
= 1 000 000 - 19544 + 1000
= 980 456 + 1000
= 981 456
b) 8/15 + 4/7 + 14/30 + 12/21 + 5
= ( 8/15 + 14/30 ) + ( 4/7 + 12/21 ) + 5
= ( 16/30 + 14/30 ) + ( 12/21 + 12/21 ) + 5
= 30/30 + 24/21 + 5
= 1 + 24/21 + 5
= ( 1 + 5 ) + 24/21
= 6 + 24/21
= 150/21
= 50/7
a) 1 + 1/4 + 1/8 + 1/16
= 16/16 + 4/16 + 2/16 + 1/16
= 23/16
b) 2 - 1/8 - 1/12 - 1/16
= 96/48 - 6/46 - 4/48 - 3/48
= 83/48
c) 4/99 × 18/5 : 12/11 + 3/5
= 8/55 : 12/11 + 3/5
= 2/15 + 3/5
= 2/15 + 9/15
= 11/15
d) (1 - 3/4) × (1 + 1/3) : (1 - 1/3)
= 1/4 × 4/3 : 2/3
= 1/3 : 2/3
= 2
\(\dfrac{3}{8}\times\dfrac{5}{12}+\dfrac{5}{8}\times\dfrac{5}{12}\)
\(=\dfrac{5}{12}\times\left(\dfrac{3}{8}+\dfrac{5}{8}\right)\)
\(=\dfrac{5}{12}\times1\)
\(=\dfrac{5}{12}\)
3/8 x 5/12 + 5/8 x 5/12
= 5/12 x (3/8 + 5/8 )
= 5/12 x 1
= 5/12