Tính
a ) 2 3 + 3 4 ; b ) 9 4 + 3 5 c ) 2 5 + 4 7 ; d ) 3 5 + 4 3
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\(\dfrac{2}{9}+\dfrac{3}{9}=\dfrac{5}{9}\)
\(\dfrac{3}{15}+\dfrac{5}{5}=\dfrac{1}{5}+\dfrac{5}{5}=\dfrac{6}{5}\)
\(\dfrac{4}{25}+\dfrac{3}{100}=\dfrac{16}{100}+\dfrac{3}{100}=\dfrac{19}{100}\)
\(\dfrac{4}{9}+\dfrac{3}{2}=\dfrac{8}{18}+\dfrac{27}{18}=\dfrac{35}{18}\)
Bài 1:
a, 3\(\dfrac{2}{5}\) - \(\dfrac{1}{2}\)
= \(\dfrac{17}{5}\) - \(\dfrac{1}{2}\)
= \(\dfrac{34}{10}\) - \(\dfrac{5}{10}\)
= \(\dfrac{29}{10}\)
b, \(\dfrac{4}{5}\) + \(\dfrac{1}{5}\) x \(\dfrac{3}{4}\)
= \(\dfrac{4\times4}{5\times4}\) + \(\dfrac{1\times3}{5\times4}\)
= \(\dfrac{16}{20}\) + \(\dfrac{3}{20}\)
= \(\dfrac{19}{20}\)
c, 4\(\dfrac{4}{9}\) : 2\(\dfrac{2}{3}\) + 3\(\dfrac{1}{6}\)
= \(\dfrac{40}{9}\) : \(\dfrac{8}{3}\) + \(\dfrac{19}{6}\)
= \(\dfrac{5}{3}\) + \(\dfrac{19}{6}\)
= \(\dfrac{10}{6}\) + \(\dfrac{19}{6}\)
= \(\dfrac{29}{6}\)
Bài 2:
3\(\dfrac{2}{5}\) + 2\(\dfrac{1}{5}\)
= \(\dfrac{17}{5}\) + \(\dfrac{11}{5}\)
= \(\dfrac{28}{5}\)
b, 7\(\dfrac{1}{6}\) : 5\(\dfrac{2}{3}\)
= \(\dfrac{43}{6}\) : \(\dfrac{17}{3}\)
= \(\dfrac{43}{34}\)
a: =91/105+60/105-101/105
=50/105=10/21
c: \(\dfrac{3}{4}\cdot\dfrac{5}{2}\cdot\dfrac{7}{6}=\dfrac{3}{6}\cdot\dfrac{7}{2}\cdot\dfrac{5}{4}=\dfrac{1}{2}\cdot\dfrac{7}{2}\cdot\dfrac{5}{4}=\dfrac{35}{16}\)
d: =2-2/9
=18/9-2/9
=16/9
e: =24/36-9/36+8/36
=23/36
g: =5/2+1/2
=3
2:
a: =4+3/8+5+2/3
=9+3/8+2/3
=216/24+9/24+16/24
=216/24+25/24
=241/24
b; =2+3/8+1+1/4+3+6/7
=6+3/8+1/4+6/7
=6+5/8+6/7
=419/56
c: \(=2+\dfrac{3}{8}-1-\dfrac{1}{4}+5+\dfrac{1}{3}\)
=6+3/8-1/4+1/3
=6+1/8+1/3
=6+11/24
=155/24
d: \(=3+\dfrac{5}{6}+6\cdot\dfrac{13}{6}\)
=3+13+5/6
=16+5/6
=101/6
e: =3+1/2+4+5/7-5-5/14
=3+4-5+1/2+5/7-5/14
=2+7/14+10/14-5/14
=2+12/14
=2+6/7=20/7
f: =9/2+1/2:11/2
=9/2+1/11
=99/22+2/22=101/22
2:
a: =4+3/8+5+2/3
=9+3/8+2/3
=216/24+9/24+16/24
=216/24+25/24
=241/24
b; =2+3/8+1+1/4+3+6/7
=6+3/8+1/4+6/7
=6+5/8+6/7
=419/56
c: \(=2+\dfrac{3}{8}-1-\dfrac{1}{4}+5+\dfrac{1}{3}\)
=6+3/8-1/4+1/3
=6+1/8+1/3
=6+11/24
=155/24
d: \(=3+\dfrac{5}{6}+6\cdot\dfrac{13}{6}\)
=3+13+5/6
=16+5/6
=101/6
e: =3+1/2+4+5/7-5-5/14
=3+4-5+1/2+5/7-5/14
=2+7/14+10/14-5/14
=2+12/14
=2+6/7=20/7
f: =9/2+1/2:11/2
=9/2+1/11
=99/22+2/22=101/22
a, 4/9 +1/2 = 17/18
b, 3/8 + 1/2 = 7/8
c, 9/8 + 3/5 = 69/40
d, 5 - 3/4 = 17/4
a. 4/9 + 1/2 = 17/18
b. 3/8 + 1/2 = 7/8
c. 9/8 + 3/5 = 69/40
d. 5 - 3/4 = 17/4
a) 2/3 + 3/4 = 8/12 + 9/12 = 17/12.
b) 2/3 x 9/5 = 18/15.
c) 2/3 : 3/4 = 2/3 x 4/3 = 8/9
d) 4/5 - 1/3 = 12/15 - 5/15 = 7/15
a ) 2/5 + 4/5 x 6/5 = 2/5+24/25 = 34/25
b ) 7/3 - 2/3 x 4/5 = 7/3 - 8/15 = 9/5
c ) 6/5 : 10 x 5/2 = 6/5 x 1/10 x 5/2 = 3/10
d ) 4 : 8/9 + 3/4 = 9/2 + 3/4 = 21/4