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1,x×1/2 + 3/2 × x = 4/5
X × (1/2 + 3/2 ) = 4/5
X × 2 = 4/5
4/5 : 2 = x
X = 2/5
2,
Số tròn trăm lớn nhất có 4 chữ số là :9900
Số lớn có 4 chữ số là : 9999
Tổng 2 số là :
9900 × 2 = 19 800
Số bé là :
19 800 - 9 999 = 9 801
3,
A)4/15 × 7/9 + 4/15 × 2/9 = 4/15 ×(7/9 +2/9)
= 4/15 ×1 = 4/15
B)13 / 19 × 23 /11 - 13/19 × 8/11 - 13 / 19 × 4/11
=13/19 × (23/11 - 8/11 - 4/11)
= 13/19 × 1
= 13/19
13/4 + 3/4 x 8= = 13/4 + 6 = 13/4 + 24/4 = 37/4
13/7 - 5 : 10/3= 13/7 - 5 x 3/10 = 13/7 - 3/2 = 26/14 - 21/14 =5/14
a) 1/2x(3/4+2/5)
1/2x23/20
23/40
b) 3/4:(8/9+16/3)
3/4:56/9
27/224
c) 1/5:1/10-1/3
2-1/3
5/3
d) 3/4x(20/9-8/15)
3/4x76/45
19/15
e) 1/7:5/14-3/2
=2/5-3/2
-11/10 ( Chị nghĩ lớp 4 chưa học đến số âm nên em xem lại đề nhé)
g) 3/2x(11/6-5/12)
3/2x17/12
17/8
a)\(\frac{1}{2}x\left(\frac{3}{4}+\frac{2}{5}\right)\)
\(=\frac{1}{2}x\left(\frac{15}{20}+\frac{8}{20}\right)\)
\(=\frac{1}{2}x\frac{23}{20}\)
\(=\frac{23}{40}\)
b)\(\frac{3}{4}:\left(\frac{8}{9}+\frac{16}{3}\right)\)
\(=\frac{3}{4}:\left(\frac{8}{9}+\frac{48}{9}\right)\)
\(=\frac{3}{4}:\frac{56}{9}\)
\(=\frac{3}{4}x\frac{9}{56}\)
\(=\frac{27}{224}\)
c) \(\frac{1}{5}:\frac{1}{10}-\frac{1}{3}\)
\(=\frac{1}{5}x10-\frac{1}{3}\)
\(=2-\frac{1}{3}\)
\(=\frac{6}{3}-\frac{1}{3}=\frac{5}{3}\)
d) \(\frac{3}{4}x\left(\frac{20}{9}-\frac{8}{15}\right)\)
\(=\frac{3}{4}x\left(\frac{100}{45}-\frac{24}{45}\right)\)
\(=\frac{3}{4}x\frac{76}{45}\)
\(=\frac{19}{5}\)
e) \(\frac{1}{7}:\frac{5}{14}-\frac{3}{2}\)
\(=\frac{1}{7}x\frac{14}{5}-\frac{3}{2}\)
\(=\frac{2}{5}-\frac{3}{2}\)
\(=\frac{4}{10}-\frac{15}{10}\)
\(=\frac{-11}{10}\)
g) \(\frac{3}{2}x\left(\frac{11}{6}-\frac{5}{12}\right)\)
\(=\frac{3}{2}x\left(\frac{22}{12}-\frac{5}{12}\right)\)
\(=\frac{3}{2}x\frac{17}{12}\)
=\(=\frac{17}{8}\)
a) 4/9 x ( 3/5 + 8/5 - 2/10 )
= 4/9 x 1
=4/9
b) ( 312 + 325 - 247 ) : 13
= 390 : 13
= 30
X + 5/9 = 4/3
X = 4/3 - 5/9
X = 7/9
X - 4/9 = 1/2
X = 1/2 + 4/9
X = 17/18
6/13 + X = 7/6
X = 7/6 - 6/13
X = 55/78
13/5 - X = 5/6
X = 13/5 - 5/6
X= 53/30
X + 5/9 = 4/3
x = 4/3 - 5/9
x = 7/9
X - 4/9 = 1/2
x = 1/2 + 4/9
x = 17/18
6/13 + X = 7/6
x = 7/6 - 6/13
x - 55/78
13/5 - X = 5/6
x = 13/5 - 5/6
x = 53/30
a. 3/5 -1/5 x 10/13
= 3/5 - 2/13
= 29/65
b. 1/2 + 3/8 : 3/4
= 1/2 + 1/2
= 1
c. (3/5 - 3/20) x4/5
= 9/20 x 4/5
= 9/25
\(a,\frac{3}{5}-\frac{1}{15}x\frac{10}{13}\)
=3/5-2/39
=107/195
b,1/2+3/8:3/4
=1/2+1/2
=1
c,(3/5-3/20)x4/5
=9/20x4/5
=9/25
\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
= \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
= \(1-\frac{1}{7}\)
= \(\frac{7}{7}-\frac{1}{7}\)
= \(\frac{6}{7}\)
2) \(\frac{7}{4}-x.\frac{4}{3}=\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{7}{4}-\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{133}{76}-\frac{20}{76}\)
\(x.\frac{4}{3}=\frac{113}{76}\)
\(x=\frac{113}{76}:\frac{4}{3}\)
\(x=\frac{399}{304}\)
VẬY \(x=\frac{399}{304}\)
b) \(\left(x+\frac{3}{4}\right).\frac{5}{7}=\frac{10}{9}\)
\(\left(x+\frac{3}{4}\right)=\frac{10}{9}:\frac{5}{7}\)
\(x+\frac{3}{4}=\frac{14}{9}\)
\(x=\frac{14}{9}-\frac{3}{4}\)
\(x=\frac{29}{36}\)
Vậy \(x=\frac{29}{36}\)
c) \(x.\frac{1}{2}+\frac{3}{2}.x=\frac{4}{5}\)
\(x.\left(\frac{1}{2}+\frac{3}{2}\right)=\frac{4}{5}\)
\(x.2=\frac{4}{5}\)
\(x=\frac{4}{5}:2\)
\(x=\frac{2}{5}\)
Vậy \(x=\frac{2}{5}\)
Chúc bạn học tốt !!!
\(\left(\frac{9}{19}.\frac{2}{3}+\frac{1}{2}\right).\left(\frac{10}{13}-\frac{2}{4}.\frac{1}{3}\right)\)
\(=\left(\frac{6}{19}+\frac{1}{2}\right).\left(\frac{10}{13}-\frac{1}{6}\right)\)
\(=\frac{31}{38}.\frac{47}{78}=\frac{1457}{2964}\)