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\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}\) \(+\frac{36}{60}+\frac{49}{70}+\frac{64}{80}+\frac{81}{90}\)
\(=\frac{1}{10}+\frac{1}{5}+\frac{3}{10}+\frac{2}{5}+\frac{1}{2}+\frac{3}{5}+\frac{7}{10}+\frac{4}{5}+\frac{9}{10}\)
\(=\left(\frac{1}{10}+\frac{9}{10}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{3}{10}+\frac{7}{10}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)+\frac{1}{2}\)
\(=1+1+1+1+0,5\)
\(=4+0,5\)
\(=4,5\)
tính bằng cách thuận tiện nhất
a) (125*36) : (5*9)
b) 6/16+8/18+10/16+10/18
c)5,6*2 +2,8*8+11,2*2-48,5
a,(125*36):(5*9)=(125x40-125*4):45=(5000-500):45=4500:45=100
b,\(\frac{6}{16}+\frac{8}{18}+\frac{10}{16}+\frac{10}{18}\)\(=\left(\frac{6}{16}+\frac{10}{16}\right)+\left(\frac{8}{18}+\frac{10}{18}\right)\)\(=\frac{16}{16}+\frac{18}{18}=1+1=2\)
c,5,6*2+2,8*8+11,2*2-48,5=5,6*2+2,8*2*4+5,6*2*2-48,5=5,6*2+5,6*4+5,6*4-48,5
=5,6*(2+4+4)-48,5=5,6x10-48,4=56-48,5=7,5
\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)
=\(\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)
=\(\frac{9}{10}\)
\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}=\frac{1}{10}+\frac{1}{10}+....+\frac{1}{10}=\frac{9}{10}\)
\(1-4+7-10+13-16+...+103-106+109\)
\(=\left(1+7+13+...+103+109\right)-\left(4+10+16+...+106\right)\)
\(=\left(\left(1+109\right)\times19:2\right)-\left(\left(106+4\right)\times18:2\right)\)
\(=1045-990\)
\(=55\)
Chúc bn học tốt!!!!!!
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
\(\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+\frac{9}{90}\)
\(=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)
\(=\frac{1}{10}\times9\)
\(=\frac{9}{10}\)
a)2×4,8× 0,5 +4× 16× 0,25+ 20: 10× 0,5
=(2×0,5)×4,8+(4×0,25)×16+(2×0,5)
= 4,8 + 16 +1
=21,8
b)12,5 × 3,14 ×8 +16 ×0,125 × 1,57
= 0,125×100×3,14×8+16×0,125×1,57
=(0,125×3,14×8+8×2×0,125×1,57)×100
=[0,125×3,14×8+8×0,125×(1,57×2)]×100
=[0,125×3,14×8+8×0,125×3,14]×100
= [(0,125×3,14×8)×2]×100
=6,28×100
=628
a 15,46+22,91+4,54+77,09 b (16/30+9/10)+21/10
=(15,46+4,54)+(22,91+77,09) =16/30+(9/10+21/10)
=20+100 =16/30+30
=120 =53/15
nhớ k cho mình nhé
a, 15,46 + 22,91 + 4,54 + 77,09
= ( 15,46 + 4,54 ) + ( 22,91 + 77,09 )
= 20 + 100
= 120
b, ( 16/30 + 9/10 ) + 21/10
= 16/30 + 9/10 + 21/10
= 16/30 + 3
= 16/30 + 30/30
= 46/30