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\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)
=\(\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)
=\(\frac{9}{10}\)
\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}=\frac{1}{10}+\frac{1}{10}+....+\frac{1}{10}=\frac{9}{10}\)
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rút gọn mấy phân số trên thì còn
=1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10
=9x1/10
=9/10
\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)
\(=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)
\(=\frac{1}{10}\times9\)
\(=\frac{9}{10}\)
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\(a,50\%+\dfrac{7}{12}-\dfrac{1}{2}\\ =\dfrac{1}{2}+\dfrac{7}{12}-\dfrac{1}{2}\\ =\left(\dfrac{1}{2}-\dfrac{1}{2}\right)+\dfrac{7}{12}\\ =\dfrac{7}{12}\\ b,2022\times67+2022\times43-2022\times10\\ =2022\times\left(67+43-10\right)\\ =2022\times100\\ =202200.\\ c,125-25:3\times12\)
\(=25\times5-25:3\times12\\ =25\times\left(5-\dfrac{1}{3}\right)\times12\\ =25\times\dfrac{14}{3}\times12\\ =1400\)
a,50%+127−21=21+127−21=(21−21)+127=127b,2022×67+2022×43−2022×10=2022×(67+43−10)=2022×100=202200.c,125−25:3×12
=25×5−25:3×12=25×(5−13)×12=25×143×12=1400=25×5−25:3×12=25×(5−31)×12=25×314×12=1400
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Tìm tổng các chữ số :
( 50 - 1 ) : 1 +1 = ....
Tổng dãy số là;
( 1 +49 ) . ( kq của phép tính đầu ) -1 : 2 + 50 = ....
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Đổi 4,2h = 4h 12' 3,25h = 3h 15'
= ( 3h x 7 + 4h + 3h x 3 - 2h ) + ( 15' x 7 + 12' + 15' x 3 - 12' )
= ( 3h x ( 7 + 3 ) + 4h - 2h ) + ( 15' x ( 7 + 3 ) + 12' - 12' )
= 32h + 150'
= 32h + 2h + 30'
= 34h 30'
HT
Do 50%=1/2 nên bt sẽ\(=\frac{1}{2}+\frac{7}{12}-\frac{1}{2}=\frac{7}{2}\)
50 % + 7/12 -1/2 = 5/10 + 7/12 - 1/2
= 1/2 + 1/12
= 7/12