c1:\(\left(\frac{1}{2}+\frac{3}{4}+\frac{4}{5}\right):3\)
\(=\left(\frac{10}{20}+\frac{15}{20}+\frac{16}{20}\right):3\)
\(=\frac{41}{20}:3=\frac{41}{60}\)
c2: \(\left(\frac{1}{2}+\frac{3}{4}+\frac{4}{5}\right):3\)
\(=\frac{1}{6}+\frac{1}{4}+\frac{4}{15}\)
\(=\frac{10}{60}+\frac{15}{60}+\frac{16}{60}\)
\(=\frac{41}{60}\)
\(\left(\frac{1}{2}+\frac{3}{4}+\frac{4}{5}\right):3\)
\(=\left(\frac{10}{20}+\frac{15}{20}+\frac{16}{20}\right).\frac{1}{3}\)
\(=\frac{41}{20}.\frac{1}{3}\)
\(=\frac{41}{60}\)
Lưu ý: dấu "." là dấu nhân