Tính :
\(12+13+14+15-45+25\)
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\(a.13.\left(78+22\right)=13.100=1300\)
\(b.25.70+28.25+25.2=25.\left(70+28+2\right)=25.100=2500\)
\(c.\dfrac{15.3.14.2.19}{19.14.15}=6\)
\(d.\dfrac{132.70.60}{12.35.20}=\dfrac{11.12.35.2.20.3}{12.35.20}=66\)
25 + 25 + 25 + 25 + 25 + 25 +25 + 25=25x8=200
45 + 45 + 45 + 45 + 15 + 15 + 15 + 15=(45x4)+(15x4)=180+60=240
a)-13-10-8-12
=-(13+10+8+12)=>-43
b)-14-7-12-21
=-(14+7+12+21)=>-54
c)-5-9-11-24
=-(5+9+11+24)=>-49
d)-6-8-13-17
=-(6+8+13+17)=>-44
e)-10-14-16-15
=-(10+14+16+15)=>-55
g)-3-7-25-45
=-(3+7+25+45)=>-80
tick cho mk nha bạn
Lời giải:
$1+2+3+....+25$
$=(1+25)+(2+24)+(3+23)+(4+22)+(5+21)+(6+20)+(7+19)+(8+18)+(9+17)+(10+16)+(11+15)+(12+14)+13$
$=\underbrace{26+26+26+...+26}_{12}+13$
$=26\times 12+13=325$
\(\frac{14}{15}\cdot1.5-\left(\frac{21}{45}+25\%\right)\cdot\frac{24}{43}-3\)
\(=1.4-\left(\frac{21}{45}+\frac{1}{4}\right)\cdot\frac{24}{43}-3\)
\(=1.4-\frac{43}{60}\cdot\frac{24}{43}-3\)
\(=1.4-0.4-3\)
\(=-2\)
\(\frac{12}{13}:3=\frac{12}{13}\cdot\frac{1}{3}=\frac{4}{13}\)
\(1,=38-42+14-25+27+15=27\)
\(2,=12+21-23+21-10=21\)
\(3,=57-725-605+53=-1220\)
\(4,=55+45+15-15+55-45=110\)
12+13+14+15-45+25
=25+14+15-45+25
=39+15-45+25
=54-45+25
=9+25
=34
12 + 13 + 14 + 15 - 45 + 25 = 34
k nha