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( 3/8 + 2/8) +1/8= 3/8 + 2/8 +1/8= 3/8 + 3/8= 3/4
3/8 + (2/8 +1/8)= 3/8 + 2/8 +1/8= 3/8 + 3/8= 3/4
( 3/8 + 2/8) + 1/8....3/8+(2/8+1/8)= 3/4+.....+3/4
\(\left(\frac{3}{8}+\frac{2}{8}\right)+\frac{1}{8}=\frac{3}{8}+\left(\frac{2}{8}+\frac{1}{8}\right)=\frac{3}{8}+\frac{3}{8}=\frac{6}{8}=\frac{3}{4}\) (tính chất kết hợp)
\(\Rightarrow\left(\frac{3}{8}+\frac{2}{8}\right)+\frac{1}{8}=\frac{3}{8}+\left(\frac{1}{8}+\frac{2}{8}\right)\)
2/15 x 3/8 + 3/8 x 2/3 + 3/8 : 5
= 2/15 x 3/8 + 3/8 x 2/3 + 3/8 x 1/5
= 3/8 x ( 2/15 + 2/3 + 1/5 )
= 3/8 x 1
= 3/8
~ Hok tốt ~
#Minh#
\(a)\frac{3}{8}+\frac{2}{5}+\frac{5}{8}=\left(\frac{3}{8}+\frac{5}{8}\right)+\frac{2}{5}=1+\frac{2}{5}=\frac{7}{5}\)
\(b)\frac{5}{7}.\frac{2}{3}.\frac{14}{15}=\frac{5.2.14}{7.3.15}=\frac{4}{9}\)
\(c)\frac{3}{8}+\frac{2}{5}.\frac{5}{8}=\frac{3}{8}+\frac{1}{4}=\frac{3}{8}+\frac{2}{8}=\frac{5}{8}\)
\(d)\frac{11}{15}-\left(\frac{2}{3}-\frac{1}{5}\right)=\frac{11}{15}-\frac{7}{15}=\frac{4}{15}\)
~Học tốt~
\(a)\frac{3}{8}+\frac{2}{5}+\frac{5}{8}=\left(\frac{3}{8}+\frac{5}{8}\right)+\frac{2}{5}=1+\frac{2}{5}=\frac{7}{5}\)
\(b)\frac{5}{7}.\frac{2}{3}.\frac{14}{15}=\frac{5.2.14}{7.3.15}=\frac{4}{9}\)
\(c)\frac{3}{8}+\frac{2}{5}.\frac{5}{8}=\frac{3}{8}+\frac{1}{4}=\frac{3}{8}+\frac{2}{8}=\frac{5}{8}\)
\(d)\frac{11}{15}-\left(\frac{2}{3}-\frac{1}{5}\right)=\frac{11}{15}-\frac{7}{15}=\frac{4}{15}\)
~Học tốt~
a) \(\frac{3}{8}+\frac{2}{5}+\frac{5}{8}=\frac{3}{8}+\frac{5}{8}+\frac{2}{5}=\frac{3+5}{8}+\frac{2}{5}\)
\(=1+\frac{2}{5}=\frac{5}{5}+\frac{2}{5}=\frac{7}{5}\)
b) \(\frac{5}{7}\times\frac{2}{3}\times\frac{14}{15}=\frac{5}{7}\times\frac{14}{15}\times\frac{2}{3}=\frac{5\times2\times7}{7\times3\times5}\times\frac{2}{3}\)
\(=\frac{2}{3}\times\frac{2}{3}=\frac{4}{9}\)
c) \(\frac{3}{8}+\frac{2}{5}\times\frac{5}{8}=\frac{3}{8}+\frac{2\times5}{5\times8}=\frac{3}{8}+\frac{2}{8}\)
\(=\frac{5}{8}\)
d) \(\frac{11}{15}-\left(\frac{2}{3}-\frac{1}{5}\right)=\frac{11}{15}-\frac{2}{3}+\frac{1}{5}=\frac{11}{15}-\frac{2\times5}{3\times5}+\frac{3\times1}{3\times5}\)
\(=\frac{11}{15}-\frac{10}{15}+\frac{3}{15}=\frac{11-10+3}{15}=\frac{4}{15}\)
\(1-\)\(a,\frac{7}{8}-\frac{2}{3}=\frac{21}{24}-\frac{16}{24}=\frac{5}{24}\)
\(b,\frac{7}{8}-\frac{2}{3}\times\frac{3}{4}=\frac{7}{8}-\frac{1}{2}=\frac{7}{8}-\frac{4}{8}=\frac{3}{8}\)
\(2-\)\(a,\frac{5}{8}-x=\frac{5}{9}\)
\(x=\frac{5}{8}-\frac{5}{9}\)
\(x=\frac{5}{72}\)
\(b,\frac{3}{4}:x=\frac{2}{5}\)
\(x=\frac{3}{4}:\frac{2}{5}\)
\(x=\frac{15}{8}\)
8/15+2/3=18/15=6/5 3/8+4/8=7/8 tính thuận tiện: 3/2+2/3+4/3=3/2+(2/3+4/3)=3/2+2=7/2 3/5+7/5+3/4=(3/5+7/5)+3/4=2+3/4=11/4 hình như cái đầu tiên chép sai đề????????????????
2/3-3/8
=16/24-9/24
=7/24
\(\frac{2}{3}-\frac{3}{8}\)
\(=\frac{16}{24}-\frac{9}{24}\)
\(=\frac{7}{24}\)
#H