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thôi bọn mềnh cũng chệu boạn nhóe

12233455667889910

giúp zì vậy bn

bằng 621 mét vuông

(54 x 23) : 2 = 621 (m²)

45x-38x=1505

=>7x=1505

=>x=215

X*(45-38)=1505

X*7=1505

X=1505:7

X=215

13dm² 7cm²=1307cm²

ơ sao ko mở sgk ra mà xem cách đổi

4:

a: A=1/3(1+1/2+...+1/64)

Đặt B=1+1/2+...+1/64

=>2B=2+1+...+1/32

=>B=2-1/64=127/64

=>A=1/3*127/64=127/192

b: =5/2(1-1/3+1/3-1/5+...+1/11-1/13)

=5/2*12/13

=60/26=30/13

chữ xấu dữ vậy

`= (167 xx 198 + 98)/(167 xx 198 + 198 - 100)`

`= (167 xx 198 + 98)/(167 xx 198 + 98)`

`= 1`.

giúp ik

a,\(\dfrac{2}{5}+\dfrac{1}{10}=\dfrac{4}{10}+\dfrac{1}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)

\(b,3-\dfrac{1}{2}=\dfrac{3}{1}-\dfrac{1}{2}=\dfrac{6}{2}-\dfrac{1}{2}=\dfrac{5}{2}\)

\(c,\dfrac{7}{12}x\dfrac{12}{21}=\dfrac{1}{3}\)

\(d,4:\dfrac{2}{3}=\dfrac{4}{1}:\dfrac{2}{3}=\dfrac{4}{1}x\dfrac{3}{2}=\dfrac{6}{1}=6\)

a) \(\dfrac{2}{5}+\dfrac{1}{10}=\dfrac{4}{10}+\dfrac{1}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)

b) \(3-\dfrac{1}{2}=\dfrac{6}{2}-\dfrac{1}{2}=\dfrac{5}{2}\)

c) \(\dfrac{7}{12}\times\dfrac{12}{21}=\dfrac{7}{21}=\dfrac{1}{3}\)

d) \(4:\dfrac{2}{3}=4\times\dfrac{3}{2}=6\)

\(=11\cdot\dfrac{16}{55}\cdot\dfrac{15}{8}=\dfrac{11\cdot5}{55}\cdot\dfrac{16}{8}\cdot3=2\cdot3=6\)

= ( 3233 + 6767) + ( 902 + 1098 )

= 10000 + 2000

= 12000

\(\text{= ( 3233 + 6767) + ( 902 + 1098 ) = 10000 + 2000 = 12000}\)