70+70+70+70+7070+70+70+70+7070+70+70+70+7070+70+7070+70+70+70+7070+70+70+70+70+70+70+70+70=

=70*22 + 7070*5

=1540 + 35350

=36890 nha bạn

ủng hộ mk nha!

 70x22+7070x5

=(70x22)+(7070x5)

=1540+35350

=36890

a) \(\left(55-27\right)+\left(27+30-55\right)\)

\(=55-27+27+30-55\)

\(=\left(55-55\right)+\left(-27+27\right)+30\)

\(=30\)

b) \(\left(75+35+15\right)-\left(15-75+35\right)\)

\(=75+35+15-15+75-35\)

\(=\left(75+75\right)+\left(35-35\right)+\left(15-15\right)\)

\(=75+75\)

\(=150\)

c) \(\left(2015-79+19\right)-\left(2020+80-91\right)\)

\(=2015-79+19-2020-80+91\)

\(=\left(2015-79\right)+\left(19+91\right)-\left(2020+80\right)\)

\(=1936+110-2100\)

\(=-54\)

\(a,\dfrac{20}{30}=\dfrac{30}{45}v\text{ì}20.45=30.30=900\\ b,\dfrac{-25}{35}=\dfrac{-55}{77}v\text{ì}:\left(-25\right).77=35.\left(-55\right)=-1925\)

5 - 10 + 15 - 20 + 25 - 30 + 35 - 40 + 45 - 50 + 55

= -5 + -5 + -5 + -5 + -5 + 55

= -25 + 55

= 30

= 30 nha bạn

30 !!!

585

(15+75)+(20+70)+(25+65)+(30+60)+(35+55)+(40+50)+45
= 90+90+90+90+90+90+45
= 90.6+45
= 540+45=585

Số số hạng là:

(75-15):5+1=13(số)

Tổng là:

45x13=585

TA CÓ

55-50+45-40+35-30+25-20+15-10+5

=(55-50)+(45-40)+(35-30)+(25-20)+(15-10)+5

=5+5+5+5+5+5

=30                   K MÌNH MÌNH K LẠI

5 - 10 + 15 - 20 + 25 - 30 + 35 - 40 + 45 - 50 + 55

= (5 - 10) + (15 - 20) + (25 - 30)  + (35 - 40) + (45 - 50) + 55

= - 5 + (-5) + (-5) + (-5) + (-5) + 55

= -5 x 5 + 55

= -25 + 55

= 55 - 25

= 30

giải bằng toán lớp 2 cơ

A = 36/5

\(\dfrac{x-55}{45}+\dfrac{x-30}{35}+\dfrac{x-25}{25}+\dfrac{x-40}{15}=10\)

\(< =>\dfrac{x-55}{45}+\dfrac{x-30}{35}+\dfrac{x-25}{25}+\dfrac{x-40}{15}-10=0\)

\(< =>\dfrac{x-55}{45}-1+\dfrac{x-30}{35}-2+\dfrac{x-25}{25}-3+\dfrac{x-40}{15}-4=0\)

\(< =>\dfrac{x-100}{45}+\dfrac{x-100}{35}+\dfrac{x-100}{25}+\dfrac{x-100}{15}=0\)

\(< =>\left(x-100\right)\left(\dfrac{1}{45}+\dfrac{1}{35}+\dfrac{1}{25}+\dfrac{1}{15}\right)=0\)

\(< =>x-100=0\left(\dfrac{1}{45}+\dfrac{1}{35}+\dfrac{1}{25}+\dfrac{1}{15}\ne0\right)\)

\(< =>x=100\)

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