Thực hiện phép tính hợp lý
a , 2 9 - 5 6 + 1 3 b , 1 2 + 1 1 2 . 0 , 01 ( - 20 ) . 0 , 5
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c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)
\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)
\(=1-2=-1\)
Giải:
a)-1/12+4/3=-1/12+16/12=15/12=5/4
b)(-4/14-3/15)-(1/5-20/35-(-1)).7
=-17/35-22/35.7
=-17/35-22/5
=-171/35
c)3/5+-5/20+30/75+-7/4
=3/5+-1/4+2/5+-7/4
=(3/5+2/5)+(-1/4+-7/4)
=1+-2
=-1
d)5/6.-12/14+7/13
=-5/7+7/13
=-16/91
e)2/-9-5/-36-1/4
=-1/12-1/4
=-1/3
f)2/23+-5/12+7/18+21/23+-7/12
=(2/23+21/23)+(-5/12+-7/12)+7/18
=1+-1+7/18
=7/18
\(\left(13\frac{4}{9}+2\frac{1}{9}\right)-3\frac{4}{9}\)
\(=\left(\frac{121}{9}+\frac{19}{9}\right)-\frac{31}{9}\)
\(=\frac{140}{9}-\frac{31}{9}\)
\(=\frac{109}{9}\)
\(1,25\div\frac{15}{20}+\left(25\%-\frac{5}{6}\right)\div4\frac{2}{3}\)
\(=1,25\div\frac{3}{4}+\left(\frac{25}{100}-\frac{5}{6}\right)\div\frac{14}{3}\)
\(=1,25\times\frac{4}{3}+\left(\frac{6}{24}-\frac{20}{24}\right)\div\frac{14}{3}\)
\(=\frac{5}{3}+\frac{-14}{24}\times\frac{14}{3}\)
\(=\frac{60}{36}+\frac{-98}{36}\)
\(=\frac{-38}{36}=\frac{-19}{18}\)
a, (-20) + 16 + (-34) + 20 = [(-20) + 20] + [16 + (-34)] = 0 + (-18) = (-18) b, 12 + 3.[39 - (5 - 2)2] = 12 + 3.[39 - 32] = 12 + 3.[39 - 9] = 12 + 3.30 = 12 + 90 = 102
13 - 12 + 11 - 10 - 9 + 8 - 7 - 6 + 5 - 4 + 3 + 2 - 1
= ( 13 - 12 + 11 - 10 + 8 ) - ( 9 + 1 ) - ( 6 + 4) + ( 3 + 2 + 5 ) - 7
= 10 - 10 - 10 + 10 - 7
= ( 10 - 10 ) - ( 10 - 10 ) - 7
= 0 - 0 - 7
= - 7
4:
a: =4/15-2,9+11/15=1-2,9=-1,9
b: \(=-36,75+3,7-63,25+6,3=10-100=-90\)
c: \(=6,5+3,5-\dfrac{10}{17}-\dfrac{7}{17}=10-1=9\)
d: \(=\dfrac{13}{25}\left(-39,1-60,9\right)=\dfrac{13}{25}\left(-100\right)=-52\)
e: =-5/12-7/12-3,7-6,3=-1-10=-11
f: =2,8(-6/13-7/13)-7,2=-2,8-7,2=-10