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3 x 7/10 + 7/10 x 5 + 2 x 14/20
=3x7/10+7/10x5+2x7/10
=7/10x(3+5+2)
=7/10x10
=7
`3 xx 7/10 + 7/10 xx 5 + 14/10`
`= 3 xx 7/10 + 7/10 xx 5 + 7/10 xx 2`
`= 7/10 xx ( 3 + 5 + 2 )`
`= 7/10 xx 10`
`= 70/10 = 7`
_HT_
(7/10+7/10+14/10) x 15 = 28/10 = 14/5 rút gọn
=14/5 x 15
= 14/5
chúc bn học tốt nha !!!
10/7+9/27+8/14+5/3
=10/7+1/3+4/7+5/3
=(10/7+4/7)+(1/3+5/3)
=14/7+6/3
=2+2
=4
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+20+10
=20+20+20+20+20+20+20+20+20+20+10
=20×10+10
=200+10
=210
= ( 1 + 19 ) + ( 2 + 18 ) + ( 3 + 17 ) + (4 + 16 ) + ( 5 + 15 ) + ( 6 + 14 ) + ( 7 + 13 ) + ( 8 + 12) + ( 9+ 11 ) + 20
= 20 + 20 + 20 +20 + 20 +20 + 20 + 20 + 20 +20
= 20 x 10
= 200
tui đầu tiên đó
Bài làm :
\(a,\frac{1}{7}+\frac{3}{4}+\frac{2}{7}+\frac{4}{7}\)
\(=\left(\frac{1}{7}+\frac{2}{7}+\frac{4}{7}\right)+\frac{3}{4}\)
\(=1+\frac{3}{4}\)
\(=\frac{7}{4}\)
\(b,\frac{4}{7}:\frac{2}{5}+\frac{3}{7}:\frac{2}{5}-\frac{7}{9}\)
\(=\left(\frac{4}{7}+\frac{3}{7}\right):\frac{2}{5}-\frac{7}{9}\)
\(=1:\frac{2}{5}-\frac{7}{9}\)
\(=\frac{5}{2}-\frac{7}{9}\)
\(=\frac{31}{18}\)
Học tốt
\(a,\frac{1}{7}+\frac{3}{4}+\frac{2}{7}+\frac{4}{7}\)
\(=\left(\frac{1}{7}+\frac{2}{7}+\frac{4}{7}\right)+\frac{3}{4}\)
\(=1+\frac{3}{4}\)
\(=\frac{7}{4}\)
\(b,\frac{4}{7}:\frac{2}{5}+\frac{3}{7}:\frac{2}{5}-\frac{7}{9}\)
\(=\left(\frac{4}{7}+\frac{3}{7}\right):\frac{2}{5}-\frac{7}{9}\)
\(=1:\frac{2}{5}-\frac{7}{9}\)
\(=\frac{5}{2}-\frac{7}{9}\)
\(=\frac{31}{18}\)
\(=\frac{10}{11}-\frac{3}{7}:\frac{7}{15}:\frac{15}{14}\)
\(=\frac{10}{11}-\frac{45}{49}:\frac{15}{14}\)
\(=\frac{10}{11}-\frac{6}{7}=\frac{70}{77}-\frac{66}{77}=\frac{4}{77}\)
a, \(\frac{5}{11}\times\frac{7}{25}+\frac{15}{11}\times\frac{1}{5}\)
\(=\frac{5}{11}\times\frac{7}{25}+\frac{5}{11}\times\frac{3}{5}\)
\(=\frac{5}{11}\times\left(\frac{7}{25}+\frac{3}{5}\right)\)
\(=\frac{5}{11}\times\frac{22}{25}\)
\(=\frac{2}{5}\)
b, \(\frac{3}{7}\times\frac{25}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\frac{75}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\left(\frac{75}{19}-\frac{18}{19}\right)\)
\(=\frac{1}{7}\times3\)
\(=\frac{3}{7}\)
\(\frac{9}{10}\)+\(\frac{7}{9}\)+\(\frac{5}{8}\)+\(\frac{3}{7}+\frac{3}{5}+\frac{2}{5}+\frac{4}{7}+\frac{3}{8}+\frac{2}{9}+\frac{1}{10}\)
\(=\left(\frac{9}{10}+\frac{1}{10}\right)+\left(\frac{7}{9}+\frac{2}{9}\right)+\left(\frac{5}{8}+\frac{3}{8}\right)\)\(+\left(\frac{3}{7}+\frac{4}{7}\right)+\left(\frac{3}{5}+\frac{2}{5}\right)\)
\(=1+1+1+1+1\)
\(=5\)
9/10 + 7/9 + 5/8 + 3/7 + 3/5 + 2/5 + 4/7 + 3/8 + 2/9 + 1/10
= ( 9/10 + 1/10 ) + ( 7/9 + 2/9 ) + ( 5/8 + 3/8 ) + ( 3/7 + 4/7 ) + ( 3/5 + 2/5 )
= 1 + 1 + 1 + 1 + 1
= 5