1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/30+81/90
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NT
5
O
3
8 tháng 2 2020
Rút gọn tất cả các phân số ta có:
\(\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}+\frac{5}{10}+\frac{6}{10}+\frac{7}{10}+\frac{8}{10}+\frac{9}{10}\)
\(=\frac{1+2+3+4+5+6+7+8+9}{10}=\frac{45}{10}=\frac{9}{2}\)
SX
1
16 tháng 3 2016
1/10 + 4/20 + 9/30 + 16/40 + 25/50 + 36/60 + 49/70 + 64/80 + 81/90
= 1/10 + 2/10 + 3/10 + 4/10 + 5/10 + 6/10 + 7/10 + 8/10 + 9/10
=(1+2+3+....+9) /10
=(1+9)x9:2 /10
=45/10=4,5
chắc chắn đúng đó
NL
3
3 tháng 8 2015
\(M=\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+...+\frac{81}{90}\)
\(M=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}+...+\frac{9}{10}\)
\(M=\frac{\left(9+1\right)\cdot\left(9-1+1\right):2}{10}\)
\(M=\frac{10\cdot9:2}{10}=4,5\)
S
10 tháng 2 2023
\(\dfrac{1}{10}+\dfrac{4}{20}+\dfrac{9}{30}+\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
\(=\dfrac{1}{10}+\dfrac{1}{5}+\dfrac{3}{10}+\dfrac{2}{5}+\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{7}{10}+\dfrac{4}{5}+\dfrac{9}{10}\)
\(=\left(\dfrac{1}{10}+\dfrac{3}{10}+\dfrac{7}{10}+\dfrac{9}{10}\right)+\left(\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}\right)+\dfrac{1}{2}\)
\(=2+2+\dfrac{1}{2}\)
\(=4+\dfrac{1}{2}\)
\(=\dfrac{8}{2}+\dfrac{1}{2}=\dfrac{9}{2}\)
LP
1
15 tháng 9 2017
\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}\) \(+\frac{36}{60}+\frac{49}{70}+\frac{64}{80}+\frac{81}{90}\)
\(=\frac{1}{10}+\frac{1}{5}+\frac{3}{10}+\frac{2}{5}+\frac{1}{2}+\frac{3}{5}+\frac{7}{10}+\frac{4}{5}+\frac{9}{10}\)
\(=\left(\frac{1}{10}+\frac{9}{10}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{3}{10}+\frac{7}{10}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)+\frac{1}{2}\)
\(=1+1+1+1+0,5\)
\(=4+0,5\)
\(=4,5\)
VT
0
CT
1
19 tháng 9 2016
\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+.....+\frac{81}{90}\)
\(=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+...+\frac{9}{10}\)
\(=\frac{\left(9+1\right)\times\left(9+1-1\right):2}{10}\)
\(=\frac{10\times9:2}{10}\)
\(=\frac{45}{10}=4,5\)
23 tháng 10 2021
\(a,=\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}=\dfrac{45}{10}=4,5\\ b,=\dfrac{4}{5}\times\left(\dfrac{3}{8}+\dfrac{5}{8}-\dfrac{7}{8}\right)\times2=\dfrac{8}{5}\times\dfrac{1}{8}=\dfrac{1}{5}=0,2\)
7 tháng 1 2023
a) Rút gọn các phân số về tối giản, ta được:
\(\dfrac{1}{10}\)+\(\dfrac{2}{10}\)+\(\dfrac{3}{10}\)+\(\dfrac{4}{10}\)+\(\dfrac{5}{10}\)+\(\dfrac{6}{10}\)+\(\dfrac{7}{10}\)+\(\dfrac{8}{10}\)+\(\dfrac{9}{10}\)= kết quả là \(\dfrac{45}{10}\) ra số thập phân = \(4,5\)
b) \(\dfrac{4}{5}\) \(\times\) \(\left(\dfrac{3}{8}+\dfrac{5}{8}-\dfrac{7}{8}\right)\) = \(\dfrac{4}{5}\times\dfrac{1}{8}\) = \(\dfrac{4}{40}=\dfrac{1}{10}\)\(\div\dfrac{1}{2}\)
= \(\dfrac{2}{10}=0,2\)
\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+....+\frac{81}{90}\)
\(=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+...+\frac{9}{10}\)
\(=\frac{\left(1+2+3+.....+9\right)}{10}\)
\(=\frac{45}{10}=\frac{9}{2}\)
\(S=\frac{1}{10}+\frac{2^2}{20}+\frac{3^2}{30}+....+\frac{9^2}{90}=\frac{1}{10}+\frac{2}{10}+...+\frac{9}{10}=\frac{45}{10}=\frac{9}{2}\)