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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
| a | b | c | a x (b - c) | a x b - a x c |
|---|---|---|---|---|
| 3 | 7 | 3 | 3 x (7 - 3) = 12 | 3 x 7 - 3 x 3 = 12 |
| 6 | 9 | 5 | 6 x (9 - 5) = 24 | 6 x 9 - 6 x 5 = 24 |
| 8 | 5 | 2 | 8 x (5 - 2) = 24 | 8 x 5 - 8 x 2 = 24 |
| a | b | c | a x (b - c) | a x b - a x c |
|---|---|---|---|---|
| 3 | 7 | 3 | 3 x (7 - 3) = 12 | 3 x 7 - 3 x 3 = 12 |
| 6 | 9 | 5 | 6 x (9 - 5) = 24 | 6 x 9 - 6 x 5 = 24 |
| 8 | 5 | 2 | 8 x (5 - 2) = 24 | 8 x 5 - 8 x 2 = 24 |
Tính giá trị biểu thức a x 12 + 2,1 x b + 5 với a = 19,36 và b = 7,9 ?
Đáp số:
\(a,\dfrac{3}{2}\times\dfrac{4}{5}\times\dfrac{2}{3}\times\dfrac{15}{4}\\ =\dfrac{3\times4\times2\times15}{2\times5\times3\times4}\\ =\dfrac{3\times4\times2\times5\times3}{2\times5\times3\times4}\\ =3\)
\(b,\dfrac{6}{7}\times\dfrac{5}{8}\times\dfrac{7}{3}\times\dfrac{7}{6}\times\dfrac{8}{5}\\ =\dfrac{6\times5\times7\times7\times8}{7\times8\times3\times6\times5}\\ =\dfrac{7}{3}\)
a) \(\dfrac{3}{2}\times\dfrac{4}{5}\times\dfrac{2}{3}\times\dfrac{15}{4}\)
\(=\left(\dfrac{3}{2}\times\dfrac{2}{3}\right)\times\left(\dfrac{4}{5}\times\dfrac{15}{4}\right)\)
\(=1\times3\)
\(=3\)
b) \(\dfrac{6}{7}\times\dfrac{5}{8}\times\dfrac{7}{3}\times\dfrac{7}{6}\times\dfrac{8}{5}\)
\(=\left(\dfrac{6}{7}\times\dfrac{7}{6}\right)\times\left(\dfrac{5}{8}\times\dfrac{8}{5}\right)\times\dfrac{7}{3}\)
\(=1\times1\times\dfrac{7}{3}\)
\(=\dfrac{7}{3}\)
Chúc bạn học tốt
`a, 3/4 + 1/2 xx 7/2`
`= 3/4 + 7/4`
`=10/4`
`=5/2`
`b, 6/15 - 1/3 : 5/3`
`= 6/15 - 1/3 xx 3/5`
`= 6/15 - 3/15`
`= 3/15`
`=1/5`
`c, x-4/9 = 3/7 : 9/4`
`=> x-4/9= 3/7 xx 4/9`
`=> x-4/9= 12/63`
`=> x-4/9=4/21`
`=> x= 4/21 +4/9`
`=>x= 40/63`
`d, 7/9 xx 3/5 -1/2=1/5`
`->` sao lại bằng có `x` ko vậy ạ?
`a,`
`3/4+1/2 \times 7/2=3/4+7/4=10/4=5/2`
`b,`
`6/15 - 1/3 \div 5/3=6/15-1/5=1/5`
`c,` Tìm x?
`x-4/9=3/7 \div 9/4`
`x-4/9=4/21`
`x=4/21+4/9`
`x=40/63`
`d, 7/9x \times 3/5-1/2=1/5`
`7/9x \times 3/5=1/5+1/2`
`7/9x \times 3/5=7/10`
`7/9x=7/10 \div 3/5`
`7/9x=7/6`
`x=7/6 \div 7/9=3/2`
\(a,\dfrac{6}{11}+6+\dfrac{5}{7}=\dfrac{42+462+55}{77}=\dfrac{559}{77}\)
\(b,\dfrac{9}{8}\times\dfrac{3}{12}:\dfrac{5}{9}=\dfrac{9}{8}\times\dfrac{3}{12}\times\dfrac{9}{5}=\dfrac{243}{480}=\dfrac{81}{160}\)
\(c,\dfrac{8}{7}:4+2=\dfrac{8}{7}\times\dfrac{1}{4}+2=\dfrac{8}{28}+2=\dfrac{2}{7}+2=\dfrac{16}{7}\)
\(d,\dfrac{3}{5}+4:\dfrac{6}{4}=\dfrac{3}{5}+4\times\dfrac{4}{6}=\dfrac{3}{5}+\dfrac{8}{3}=\dfrac{49}{15}\)
a) 3/5:6/7-8/15 b)2/3+2/5-1/3 c) 4/9x3/2:2/3 d)1785+564x27
= 7/10 -8/15 =16/15-1/3 =2/3:2/3 =1785+15228
=1/6 =11/15 =1 =17013
a. 437 x (5+4)
C1: 437 x 9 = 3 933
C2: 437 x (5+4) = 437 x 5 + 437 x 4
= 2 185 + 1 748 = 3 933
b.1 375 x (3+7)
C1: 1 375 x 10 = 13 750
C2: 1 375 x (3+7) = 1 375 x 3 + 1 375 x 7
= 4 125 + 9 625 = 13 750
c. 605 x (3+6)=
C1:605 x 9 = 605 x ( 10 -1 ) = 605 x 10 - 605 x 1 = 6 050 - 605 = 5 445
C2: 605 x ( 3+6) = 605 x 3 + 605 x 6
= 1 815 + 3 630 = 5 445
d. 4 007 x (2+8)
C1: 4 007 x 10 = 40 070
C2: 4007 x (2+8) = 4 007 x 2 + 4 007 x 8
= 8 014 + 32 056 = 40 070