Tính nhẩm:
a) 2 x 3 6 : 2 6 : 3
b) 5 x 4 20 : 5 20 : 4
c) 2 x 1 2 : 2 2 : 1
d) 5 x 1 5 : 5 5 : 1
Bài 3: Tính bằng hai cách
a 1/8 x 5/6 + 5/6 x 2/3
b 7/5 x 3/4 - 1/2 x 3/4
c (5/6 + 5/8) x 2/3
a,C1
(5/6 + 5/8) x 2/3
= 35/24 x 2/3
=35/36
C2
(5/6 + 5/8) x 2/3
= 5/6x2/3 + 5/8x2/3
= 10/18 + 10/24
= 35/36
b,C1
7/5 x 3/4 - 1/2 x 3/4
= 21/20 - 3/8
= 27/40
C2
7/5 x 3/4 - 1/2 x 3/4
=3/4 x (7/5-1/2)
=3/4x9/10
=27/40
Bài 3: Tính bằng hai cách
a 1/8 x 5/6 + 5/6 x 2/3
b 7/5 x 3/4 - 1/2 x 3/4
c (5/6 + 5/8) x 2/3
a, 5/6 x (1/8x2/3)
=5/6 x 1/12
=5/72
b,(7/5 - 1/2) x 3/4
=0,9 x 3/4
=3,06
c,(5/6+5/8) x 2/3
=70/48 x 2/3
=35/36
a, 5/6 x (1/8x2/3)
=5/6 x 1/12
=5/72
b,(7/5 - 1/2) x 3/4
=0,9 x 3/4
=3,06
c,(5/6+5/8) x 2/3
=70/48 x 2/3
=35/36
Tính nhẩm:
a) 2000 x 4 x 5 36 000 : 6 : 2 30 000 : 3 x 2
b)20 000 x (10 : 5) 80 000 : (2 x 4) 15 000 : (27 : 9)
a)
2000 × 4 × 5 = 8000 × 5 = 40 000
36 000 : 6 : 2 = 6000 : 2 = 3000
30 000 : 3 x 2 = 10 000 x 2 = 20 000
b)
20 000 × (10 : 5) = 20 000 × 2 = 40 000
80 000 : (2 × 4) = 80 000 : 8 = 10 000
15 000 : (27 : 9) = 15 000 : 3 = 5000
Bài 3: Tính bằng hai cách
a 1/8 x 5/6 + 5/6 x 2/3
b 7/5 x 3/4 - 1/2 x 3/4
c (5/6 + 5/8) x 2/3
càng nhanh càng tốt vì mình đang rất gấp
a) C1
\(\dfrac{1}{8}\times\dfrac{5}{6}+\dfrac{5}{6}\times\dfrac{2}{3}=\dfrac{5}{6}\times\left(\dfrac{1}{8}+\dfrac{2}{3}\right)=\dfrac{5}{6}\times\dfrac{19}{24}=\dfrac{95}{144}\)
C2
\(\dfrac{1}{8}\times\dfrac{5}{6}+\dfrac{5}{6}\times\dfrac{2}{3}=\dfrac{5}{48}+\dfrac{10}{18}=\dfrac{95}{144}\)
b) C1
\(\dfrac{7}{5}\times\dfrac{3}{4}-\dfrac{1}{2}\times\dfrac{3}{4}=\dfrac{3}{4}\times\left(\dfrac{7}{5}-\dfrac{1}{2}\right)=\dfrac{3}{4}\times\dfrac{9}{10}=\dfrac{27}{40}\)
C2
\(\dfrac{7}{5}\times\dfrac{3}{4}-\dfrac{1}{2}\times\dfrac{3}{4}=\dfrac{21}{20}-\dfrac{3}{8}=\dfrac{27}{40}\)
c) C1
\(\left(\dfrac{5}{6}+\dfrac{5}{8}\right)\times\dfrac{2}{3}=\dfrac{35}{24}\times\dfrac{2}{3}=\dfrac{35}{36}\)
C2
\(\left(\dfrac{5}{6}+\dfrac{5}{8}\right)\times\dfrac{2}{3}=\left(\dfrac{5}{6}\times\dfrac{2}{3}\right)+\left(\dfrac{5}{8}\times\dfrac{2}{3}\right)=\dfrac{5}{9}+\dfrac{5}{12}=\dfrac{35}{36}\)
Tính bằng 2 cách
Bài 3: Tính bằng hai cách
a 1/8 x 5/6 + 5/6 x 2/3
b 7/5 x 3/4 - 1/2 x 3/4
c (5/6 + 5/8) x 2/3
giúp mình nhanh nhất có thể nha ai mà ghi kết quả thôi là mình ko tick đúng đâu nha
a: =5/6(1/8+2/3)=5/6*19/24=95/144
b: =3/4(7/5-1/2)=27/40
c: =35/24*2/3=35/36
giải hệ pt (đặt ẩn phụ )
a) x+2/x+1 + 2/y-2 =6
5/x+1 -1/y-2 =3
b) 2/2x-y +3/x-2y =1/2
2/2x-y -1/x-2y =1/18
c) 2|x-6| +3|y+1| =5
5|x-6| -4|y+1| =1
d) |x| +|y-3| =1
y - |x| =3
a: \(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{x+1+1}{x+1}+\dfrac{2}{y-2}=6\\\dfrac{5}{x+1}-\dfrac{1}{y-2}=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{1}{x+1}+\dfrac{2}{y-2}=5\\\dfrac{5}{x+1}-\dfrac{1}{y-2}=3\end{matrix}\right.\)
=>x+1=1 và y-2=1/2
=>x=0 và y=5/2
b: \(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{4}{x-2y}=\dfrac{1}{2}-\dfrac{1}{18}=\dfrac{9}{18}-\dfrac{1}{18}=\dfrac{8}{18}=\dfrac{4}{9}\\\dfrac{2}{2x-y}=\dfrac{1}{18}+\dfrac{1}{x-2y}\end{matrix}\right.\)
=>x-2y=9 và 2/2x-y=1/18+1/9=1/18+2/18=3/18=1/6
=>x-2y=9 và 2x-y=12
=>x=5; y=-2
c: \(\Leftrightarrow\left\{{}\begin{matrix}10\left|x-6\right|+15\left|y+1\right|=25\\10\left|x-6\right|-8\left|y+1\right|=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}23\left|y+1\right|=23\\\left|x-6\right|=1\end{matrix}\right.\)
=>|x-6|=1 và |y+1|=1
=>\(\left\{{}\begin{matrix}x\in\left\{7;5\right\}\\y\in\left\{0;-2\right\}\end{matrix}\right.\)
Tính nhẩm:
a) 60:2 , 70:2, 40:2, 90:3
b) Mẫu: 6 trăm : 3 = 2 trăm; Vậy 600:3= 20-0
Tính theo mẫu: 800:4 ; 400:2; 500:5
1) 2³ .x -5² x = 2( 5² + 2² ) -33. 2) 15÷ ( x +2) = (3³ +3) ÷1
3) 20÷ (x +1) = (5² +1 ) ÷13. 4) 320÷ ( x -1 ) = (5³ - 5² ) ÷4 +15
5) 240 ÷ ( x -5 ) = 2² .5² -20. 6) 70 ÷ ( x -3) = ( 3⁴ -1) ÷ 4 - 10
Giúp mình với mình Tối nay mình đi học rồi
1) \(2^3\times x-5^2\times x=2\times\left(5^2+2^2\right)-33\)
\(x\times\left(2^3-5^2\right)=2\times\left(25+4\right)-33\)
\(x\times\left(8-25\right)=2\times29-33\)
\(x\times-17=25\)
\(x=-\dfrac{25}{17}\)
2) \(15\div\left(x+2\right)=\left(3^3+3\right)\div1\)
\(15\div\left(x+2\right)=\left(27+3\right)\div1\)
\(15\div\left(x+2\right)=30\div1\)
\(15\div\left(x+2\right)=30\)
\(x+2=\dfrac{1}{2}\)
\(x=-\dfrac{3}{2}\)
3) \(20\div\left(x+1\right)=\left(5^2+1\right)\div13\)
\(20\div\left(x+1\right)=\left(25+1\right)\div13\)
\(20\div\left(x+1\right)=26\div13\)
\(20\div\left(x+1\right)=2\)
\(x+1=20\div2\)
\(x+1=10\)
\(x=9\)
4) \(320\div\left(x-1\right)=\left(5^3-5^2\right)\div4+15\)
\(320\div\left(x-1\right)=\left(125-25\right)\div4+15\)
\(320\div\left(x-1\right)=100\div4+15\)
\(320\div\left(x-1\right)=25+15\)
\(320\div\left(x-1\right)=40\)
\(x-1=8\)
\(x=9\)
5) \(240\div\left(x-5\right)=2^2\times5^2-20\)
\(240\div\left(x-5\right)=4\times25-20\)
\(240\div\left(x-5\right)=100-20\)
\(240\div\left(x-5\right)=80\)
\(x-5=30\)
\(x=35\)
6) \(70\div\left(x-3\right)=\left(3^4-1\right)\div4-10\)
\(70\div\left(x-3\right)=\left(81-1\right)\div4-10\)
\(70\div\left(x-3\right)=80\div4-10\)
\(70\div\left(x-3\right)=20-10\)
\(70\div\left(x-3\right)=10\)
\(x-3=7\)
\(x=10\)
1. tìm x
a)1/2+X=5/6 b)X+1/4=3/4
c) 3/10 +X=1/2 d) X+1/4=3/8
2. tính giá trị biểu thức
7/20 -(5/8-2/5) 9/10 - (2/5+3/10)+7/20
Bài 1:
a: x+1/2=5/6
nên x=5/6-1/2=1/3
b: x+1/4=3/4
nên x=3/4-1/4=2/4=1/2
c: x+3/10=1/2
nên x=1/2-3/10=5/10-3/10=1/5
d: x+1/4=3/8
nên x=3/8-1/4=3/8-2/8=1/8