y × 5/7 - 5/7 + 3/4 = 21/28
Viết vào chỗ chấm :
7 x 3 = ... 7 x 6 = ... 7 x 5 = ... 7 x 4 = ...
21 : 7 = ... 42 : 7 = ... 35 : 7 = ... 28 : 7 = ...
21 : 3 = ... 42 : 6 = ... 35 : 5 = ... 28 : 4 = ...
7 x 3 = 21 7 x 6 = 42 7 x 5 = 35 7 x 4 = 28
21 : 7 = 3 42 : 7 = 6 35 : 7 = 5 28 : 7 = 4
21 : 3 = 7 42 : 6 = 7 35 : 5 = 7 28 : 4 = 7
7 × 3 = 21 7 × 6 = 42 7 × 5 = 35. 7 × 4 = 28
21 : 7 = 3. 42 : 7 = 6. 35 : 7 = 5. 28 : 7 = 4
21 : 3 = 7. 42 : 6 = 7. 35 : 5 = 7. 28 : 4 = 7
Tính nhẩm:
35 : 5 =
28 : 7 =
24 : 6 =
21 : 3 =
35 : 7 =
28 : 4 =
24 : 4 =
21 : 7 =
Học sinh nhẩm và ghi kết quả như sau:
35 : 5 = 7
28 : 7 = 4
24 : 6 = 4
21 : 3 = 7
35 : 7 = 5
28 : 4 = 7
24 : 4 = 6
21 : 7 = 3
35 : 5 = 7
28 : 7 = 4
24 : 6 = 4
21 : 3 = 7
35 : 7 = 5
28 : 4 = 7
24 : 4 = 6
21 : 7 = 3
Tính theo mẫu :
Mẫu : 13/21 + 5/7 = 13/21 + 5 x 3 / 7 x 3 = 13/21 + 15/21 = 28/21
26/81 + 4/27
5/64 + 7/8
\(\dfrac{26}{81}+\dfrac{4}{27}=\dfrac{26+12}{81}=\dfrac{38}{81}\)
\(\dfrac{5}{64}+\dfrac{7}{8}=\dfrac{5+56}{64}=\dfrac{61}{64}\)
\(\dfrac{26}{81}+\dfrac{4}{27}=\dfrac{26}{81}+\dfrac{4\times3}{27\times3}=\dfrac{26}{81}+\dfrac{12}{81}=\dfrac{38}{81}\)
\(\dfrac{5}{64}+\dfrac{7}{8}=\dfrac{5}{64}+\dfrac{7\times8}{8\times8}=\dfrac{5}{64}+\dfrac{56}{64}=\dfrac{61}{64}\)
a) 7/-25+8/25 ; 4/5+4/-18 ; 7/21+9/-36
b) 12/20-2/5 ; 2/3-(-5/6) ; 6-3/20
c)2/21*(-7/3) ; 27/28*(-21) ; -15/7*(-14/25)
a) \(\dfrac{7}{-25}+\dfrac{8}{25}=\dfrac{-7}{25}+\dfrac{8}{25}=\dfrac{1}{25}\)
\(\dfrac{4}{5}+\dfrac{4}{-18}=\dfrac{4}{5+\left(-18\right)}=\dfrac{4}{-13}=\dfrac{-4}{13}\)
\(\dfrac{7}{21}+\dfrac{9}{-36}=\dfrac{1}{3}+\dfrac{1}{-4}=\dfrac{1}{3+\left(-4\right)}=\dfrac{1}{-1}=1\)
b) \(\dfrac{12}{20}-\dfrac{2}{5}=\dfrac{12}{20}+\left(\dfrac{-2}{5}\right)=\dfrac{3}{5}+\dfrac{-2}{5}=\dfrac{3+\left(-2\right)}{5}=\dfrac{1}{5}\)
\(\dfrac{2}{3}-\dfrac{-5}{6}=\dfrac{2}{3}+\dfrac{5}{6}=\dfrac{4}{6}+\dfrac{5}{6}=\dfrac{9}{6}=\dfrac{3}{2}\)
\(6-\dfrac{3}{20}=6+\dfrac{-3}{20}=\dfrac{60}{60}+\dfrac{-9}{60}=\dfrac{51}{60}\)
c) \(\dfrac{2}{21}.\dfrac{-7}{3}=\dfrac{2.\left(-1\right)}{7.3}=\dfrac{-2}{21}\)
\(\dfrac{27}{28}.\left(-21\right)=\dfrac{27.\left(-21\right)}{28}=\dfrac{-567}{28}\)
\(\dfrac{-15}{7}.\dfrac{-14}{25}=\dfrac{-3.\left(-2\right)}{1.5}=\dfrac{6}{5}\)
Thực hiện phép tính:
A) 7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11
B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20
C) ( -2/3 + 3/7 ) : 4/5 + (-1/3 + 4/7 ) : 4/5
D) 5/9 : ( 1/11 -5/22 ) + 5/9 : ( 1/15 - 2/3 )
E) 3/14 : 1/28 -13/21 : 1/28 + 29/42 : 1/28 - 8
F) ( -40/51 x 0,32 x17/20) : 64/75
Đây là dấu x ( là nhân ) mọi người nhé
mong mn giúp em ạ
A) 7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11
=7/38.(9/11+4/11-2/11)
=7/38
B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20
=5/31.(21/25-7/10-9/20)
=5/31.(-31/100)
=-1/20
a) 7/-25+8/25 ; 4/5+4/-18 ; 7/21+9/-36
b) 12/20-2/5 ; 2/3-(-5/6) ; 6-3/20
c)2/21*(-7/3) ; 27/28*(-21) ; -15/7*(-14/25)
ai nhanh mk tk cho giup k nhe minh can gap
Thực hiện phép tính:
1, ( 136/15- 28/5+ 62/10 ) . 21/27
2, ( 3/11- 5/3 ). ( 3/4- 5/8 ) - 4/5 . 1/24
3, 6/25. 7/3+ 19/25. 7/3
Thực hiện phép tính:
1, ( 136/15- 28/5+ 62/10 ) . 21/27
2, ( 3/11- 5/3 ). ( 3/4- 5/8 ) - 4/5 . 1/24
3, 6/25. 7/3+ 19/25. 7/3
1: \(=\dfrac{272-168+186}{30}\cdot\dfrac{7}{9}=\dfrac{29}{3}\cdot\dfrac{7}{9}=\dfrac{203}{27}\)
2: \(=\dfrac{9-55}{33}\cdot\dfrac{6-5}{8}-\dfrac{4}{5}\cdot\dfrac{1}{24}=\dfrac{-4}{3}\cdot\dfrac{1}{8}-\dfrac{1}{30}=\dfrac{-1}{6}-\dfrac{1}{30}=\dfrac{-6}{30}=-\dfrac{1}{5}\)
3: \(=\dfrac{7}{3}\left(\dfrac{6}{25}+\dfrac{19}{25}\right)=\dfrac{7}{3}\cdot1=\dfrac{7}{3}\)
Tìm các số x và y biết
1) 4/x= y/21=28/49. 2) x/2=3/y. 3)42/54=7/x
4) 2/3 =y/15. 5)6/10 = 3/x =y/20
\(\dfrac{4}{x}=\dfrac{y}{21}=\dfrac{28}{49}=\dfrac{28:7}{49:7}=\dfrac{4}{9}\\ Vậy:x=\dfrac{4.9}{4}=9\\ y=\dfrac{4.21}{9}=\dfrac{28}{3}\)
\(\dfrac{x}{2}=\dfrac{3}{y}\\ \Leftrightarrow x.y=2.3=6\\ Vậy:\left[{}\begin{matrix}\left(x;y\right)=\left(1;6\right)=\left(6;1\right)\\\left(x;y\right)=\left(2;3\right)=\left(3;2\right)\end{matrix}\right.\)
\(3,\\ \dfrac{42}{54}=\dfrac{42:6}{54:6}=\dfrac{7}{9}\\ \dfrac{42}{54}=\dfrac{7}{x}=\dfrac{7}{9}\\ Vậy:x=\dfrac{7.9}{7}=9\)