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Bài 1:
câu a: 4\(\dfrac{4}{9}\) : 2\(\dfrac{2}{3}\) + 3\(\dfrac{1}{6}\)
= \(\dfrac{40}{9}\) : \(\dfrac{8}{3}\) + \(\dfrac{19}{6}\)
= \(\dfrac{5}{3}\) + \(\dfrac{19}{6}\)
= \(\dfrac{10}{6}\) + \(\dfrac{19}{6}\)
= \(\dfrac{29}{6}\)
b, (15,25 + 3,75) \(\times\) 4 + ( 20,71 + 5,29)\(\times\) 5
= 19 \(\times\) 4 + 26 \(\times\) 5
= 76 + 130
= 206
c, \(\dfrac{4}{5}\) \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{4}{5}\) \(\times\) \(\dfrac{1}{3}\) - \(\dfrac{4}{5}\) \(\times\) \(\dfrac{1}{4}\)
= \(\dfrac{2}{5}\) + \(\dfrac{4}{15}\) - \(\dfrac{1}{5}\)
= \(\dfrac{6}{15}\) + \(\dfrac{4}{15}\) - \(\dfrac{3}{15}\)
= \(\dfrac{7}{15}\)
d, 1\(\dfrac{5}{7}\) + 7\(\dfrac{3}{6}\) + 2\(\dfrac{2}{7}\) - 4\(\dfrac{3}{6}\)
= (1 + 2 + \(\dfrac{5}{7}\) + \(\dfrac{2}{7}\)) + ( 7 + \(\dfrac{3}{6}\) - 4 - \(\dfrac{3}{6}\))
= 3 + 1 + 3
= 7
khỏi chép đề nha
a\Câu 1:
200 : ( 15 - x ) = 15 + 5
200 : ( 15 - x ) = 20
15 - x = 200 : 20
15 - x = 10
x = 15 - 10
x = 5
Câu 2:
63 : ( x - 5 ) = 22 -1
63 : ( x - 5 ) = 21
x - 5 = 63 : 21
x - 5 = 3
x = 3 + 5
x = 8
\(x+\dfrac{2}{3}=\dfrac{15}{6}\times\dfrac{9}{5}\)
\(x+\dfrac{2}{3}=\dfrac{5}{3}\times\dfrac{9}{5}\)
\(x+\dfrac{2}{3}=\dfrac{9}{3}\)
\(x=\dfrac{9}{3}-\dfrac{2}{3}\)
\(x=\dfrac{7}{3}\)
______________
\(\dfrac{15}{2}-x=\dfrac{7}{4}+\dfrac{5}{2}\)
\(\dfrac{15}{2}-x=\dfrac{7}{4}+\dfrac{10}{4}\)
\(\dfrac{15}{2}-x=\dfrac{17}{4}\)
\(x=\dfrac{15}{2}-\dfrac{17}{4}\)
\(x=\dfrac{30}{4}-\dfrac{17}{4}\)
\(x=\dfrac{13}{4}\)
3 x 15 + 21 x 15 + 85 x 5
= 45 + 315 + 425
= 785
15 - 30 + 40
= 25
21 + 19 - 50 + 10
= 0
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=-\dfrac{1}{20}+2\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{12}\times\dfrac{3}{12}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=-\dfrac{9}{20}\)
\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)
\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)
\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)
\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)
\(=\dfrac{44}{20}-\dfrac{5}{20}\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)
\(=\dfrac{6}{20}-\dfrac{15}{20}\)
\(=-\dfrac{9}{20}\)
a) 2 giờ 20 phút x 2 ?1 giờ 25 phút x 3 =
b) 3 giờ 48 phút : 3 ?4 giờ 15 phút : 5 =
c) 2 giờ 15 phút x 2 + 6 giờ 15 phút : 5 =5 giờ 45 phút
d) 3 giờ 25 phút x 3 + 4 giờ 48 phút: 3 =11 giờ 51 phút
e) 211 phần 100 giờ : 6 =21 phút
f) 2,8 phút : 4 =42 giây
câu a và câu b thiếu dấu
c) 2 giờ 15 phút x 2 + 6 giờ 15 phút : 5 =5 giờ 45 phút
d) 3 giờ 25 phút x 3 + 4 giờ 48 phút: 3 =11 giờ 51 phút
e) 211 phần 100 giờ : 6 =21 phút
f) 2,8 phút : 4 =42 giây
a, x + 2/5 = 1/2
x = 1/2 + 2/5
x = 9/10 b,34/5 + x = 15/8
x = 34/5 - 15/8
x =197/40 c, x - 45/6 = 21/6 + 5/6
x - 45/6 = 26/6
x = 26/6 + 45/6
x =71/6 d,14/5 - x = 11/5 - 3/5
14/5 - x = 8/5
x = 14,5 - 8/5
x =6/5
a, x + 2/5 = 1/2
x = 1/2 + 2/5
x = 9/10
b,34/5 + x = 15/8
x = 34/5 - 15/8
x =197/40
c, x - 45/6 = 21/6 + 5/6
x - 45/6 = 26/6
x = 26/6 + 45/6
x =71/6
d,14/5 - x = 11/5 - 3/5
14/5 - x = 8/5
x = 14,5 - 8/5
x =6/5
- Làm lại.
1, 2x - 35 = 15
2x = 15 + 35
2x = 50
x = 50 : 2
x = 25.
2, 3x + 18 = 12
3x = 12 - 18
3x = -6
x = -6 : 3
x = -2.
3, / x - 1 / = 0
=> x \(\in\varnothing\).
4, -13 /x/ = - 26
/x/ = -26 : -13
=> \(\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)
Vậy x \(\in\){ 2 ; -2}.
5,4 - ( 27 - 3 ) = x - ( 13 - 4 )
4 - 24 = x - 9
-20 = x - 9
-x = 9 + 20
-x = 29
x = -29.
6, 47 - ( x + 15 ) = 21
47 - x - 15 = 21
-x - 15 = 21 - 47
-x - 15 = -26
-x = -26 + 15
-x = - 11
x = 11.
7, -5 -( 24 - x) = - 11
-5 - 24 + x = -11
-24 + x = -11 + 5
-24 + x = -6
x = -6 + 24
x = 18.
8, 6 - /x/ = 2
/x/ = 6 - 2
\(\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)
Vậy x \(\in\left\{3;-3\right\}.\)
9, 6 + /x/ = 2
/x/ = 2 - 6
=> x = -4.
2x - 35 = 15
=> 2x = 15 + 35
=> x = 50 : 2
=> x = 25
3x + 18 = 12
=> 3x = 12 - 18
=> x = ( -6 ) : 3
=> x = -2
| x - 1 | = 0
=> x - 1 = 0
=> x = 0 + 1
=> x = 1
-13 * | x | = -26
=> | x | = -26 : ( -13 )
=> | x | = 2
\(x\) \(\times\) \(\dfrac{4}{5}\) = 15
\(x\) = 15 : \(\dfrac{4}{5}\)
\(x\) = \(\dfrac{75}{4}\)
\(\dfrac{12}{25}\) \(\times\) \(x\) = \(\dfrac{4}{10}\)
\(x\) = \(\dfrac{4}{10}\) : \(\dfrac{12}{25}\)
\(x\) = \(\dfrac{5}{6}\)
`4/7 + 2/3 = 12/21 + 14/21 = 26/21`
`5/6 -3/4 = 10/12 - 9/12 = 1/12`
`3/10 xx 15/6 = 3/10 xx 5/2 = 3/4`
`7/6 : 5/4 = 7/6 xx 4/5 = 14/15`