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1. A) 225886 + 779 × 8
= 225886 + 6232
= 232118
B) 125 × 5 × 20 × 8
= (125 × 8) × (5 × 20)
= 1000 × 100
= 100000
C) 47286 : 2 + 14765
= 23643 + 14765
= 38408
D) 91428 - 23560 : 5
= 91428 - 4712
= 86716
3. A) 36 × 532 + 63 × 532 + 532
= 532 × (36 + 63 + 1)
= 532 × 100
= 53200
B) 679 × 123 + 679 - 679 × 24
= 679 × (123 + 1 - 24)
= 679 × 100
= 67900
C) 245 × 327 - 245 × 18 - 9 × 245
= 246 × (327 - 18 - 9)
= 245 × 300
= 73500
![](https://rs.olm.vn/images/avt/0.png?1311)
3. Tính bằng cách thuận tiện nhất
A, 36 x 532 + 63 x 532 + 532
= (36 + 63 + 1) x 532 = 100 x 532 = 53 200
B, 679 x 123 + 679 - 679 x 24
= 679 x (123 + 1 - 24)
= 679 x 100 = 67 900
C, 245 x 327 - 245 x 18 - 9 x 245
= 245 x (327 - 18 - 9)
= 245 x 300
= 73 500
Bài 2:
a: \(6\cdot\left(x+9845\right)=29042\)
=>\(x+9845=\dfrac{29042}{6}=\dfrac{14521}{3}\)
=>\(x=\dfrac{14521}{3}-9845=-\dfrac{15014}{3}\)
b: \(\left(x:3\right)\cdot8=8\cdot3198\)
=>\(x:3=3198\)
=>\(x=3198\cdot3=9594\)
Bài 1:
a: \(225886+779\cdot8\)
\(=225886+6232\)
\(=232118\)
b: \(125\cdot5\cdot20\cdot8\)
\(=\left(125\cdot8\right)\cdot\left(5\cdot20\right)\)
\(=1000\cdot100=100000\)
c: \(47286:2+14765\)
\(=23643+14765\)
=38408
d: \(91428-23560:5\)
\(=91428-4712\)
=86716
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a.\dfrac{12+x}{42}=\dfrac{35}{42}\Leftrightarrow12+x=35\Leftrightarrow x=23\)
\(b.\dfrac{25-x}{40}=\dfrac{3}{8}\Leftrightarrow\dfrac{25-x}{40}=\dfrac{15}{40}\Leftrightarrow25-x=15\Leftrightarrow x=10\)
\(c.\dfrac{13+x}{20}=\dfrac{3}{4}\Leftrightarrow\dfrac{13+x}{20}=\dfrac{15}{20}\Leftrightarrow13+x=15\Leftrightarrow x=2\)
\(d.\dfrac{23-x}{25}=\dfrac{20}{25}\Leftrightarrow23-x=20\Leftrightarrow x=3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)5/12 + 1/4 = \(\dfrac{5}{12}+\dfrac{3}{12}=\dfrac{8}{12}=\dfrac{2}{3}\)
b)23/5 - 11/3 = \(\dfrac{69}{15}-\dfrac{55}{15}=\dfrac{14}{15}\)
c)4/5 + 13 = \(\dfrac{4}{5}+\dfrac{65}{5}=\dfrac{69}{5}\)
d)8/5 : 1/3 = \(\dfrac{8}{5}x3=\dfrac{24}{5}\)
e)3/7 x 2 =\(\dfrac{6}{7}\)
\(a,\) \(\dfrac{5}{12}+\dfrac{1}{4}=\dfrac{5}{12}+\dfrac{3}{12}=\dfrac{8}{12}=\dfrac{2}{3}\)
\(b,\) \(\dfrac{23}{5}-\dfrac{11}{3}=\dfrac{69}{15}-\dfrac{55}{15}=\dfrac{14}{15}\)
\(c,\) \(\dfrac{4}{5}+\dfrac{1}{3}=\dfrac{12}{15}+\dfrac{5}{15}=\dfrac{17}{15}\)
\(d,\) \(\dfrac{8}{5}:\dfrac{1}{3}=\dfrac{8}{5}\times\dfrac{3}{1}=\dfrac{24}{5}\)
\(e,\) \(\dfrac{3}{7}\times2=\dfrac{3\times2}{7}=\dfrac{6}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)1/2x3/4+1/2x1/4
=1/2x(3/4+1/4)
=1/2x1
=1/2
b)3/5x1/8+3/5x23/8
=3/5x(1/8+23/8)
=3/5x3
=9/5
HT NHKK
a) 1/2 x 3/4 + 1/2 x 1/4 = 3/8 + 1/8 = 4/8
b) 3/5 x 1/8 + 3/5 x 23/8 = 3/40 + 69/40 = 72/40 = 9/5
![](https://rs.olm.vn/images/avt/0.png?1311)
TL:
8/15 x 5/6 = 40/90 = 4/9
41/20 x 3/4 = 123/80
(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43
HT
\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)
\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)
\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)
/HT\
\(A=\frac{3}{2}\times5+\frac{3}{5}\times8+\frac{3}{8}\times11+.....+\frac{3}{20}\times23+\frac{3}{23}\times26\)
\(A=\frac{3}{2}\times\frac{5}{1}+\frac{3}{5}\times\frac{8}{1}+\frac{3}{8}\times\frac{11}{1}+.....+\frac{3}{20}\times\frac{23}{1}+\frac{3}{23}\times\frac{26}{1}\)
\(A=\left(\frac{3}{2}\times\frac{5}{1}+\frac{3}{23}\times\frac{26}{1}\right)+.....+\left(\frac{3}{11}\times\frac{14}{1}+\frac{3}{14}\times\frac{17}{1}\right)\)CÓ 8 CẶP
\(A=\left(\frac{15}{2}+\frac{68}{23}\right)+.....+\left(\frac{42}{11}+\frac{51}{14}\right)\)
\(A=\left(\frac{15}{2}+\frac{68}{23}\right)+.....+\left(\frac{42}{11}+\frac{51}{14}\right)\)
CÒN LẠI TỰ GIẢI NHA
tinh tong sau bang cach hop li A Ban