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\(a.\frac{27.45+27.55}{2+4+6+...+14+16+18}=\frac{27.100}{\frac{\left(2+18\right).9}{2}}=30\)
\(b.\frac{26.108-26.12}{32-28+24-20+16-12+8-4}=\frac{26\left(108-12\right)}{\left(32-28\right).4}=\frac{26.96}{4.4}=156\)
\(c.\frac{27.4500+135.550.2}{2+4+6+...+14+16+18}=\frac{270.450+270.550}{\frac{\left(2+8\right).9}{2}}\)
\(d.\frac{48.700-24.45.20}{45-40+35-30+25-20+15-10+5}=\frac{48.700-48.450}{5.5}\)\(=\frac{48\left(700-450\right)}{25}=\frac{48.250}{25}=480\)
#ĐinhBa
\(\frac{\left(315+372\right).3+\left(372+315\right).7}{26.13+74.14}\)
\(=\frac{\left(315+372\right)\left(3+7\right)}{26.13+74.13+74}\)
\(=\frac{687.10}{13\left(26+74\right)+74}\)
\(=\frac{6870}{13.100+74}=\frac{6870}{1300+74}\)
\(=\frac{6870}{1374}\)
\(b,\frac{1978\cdot1979+1980\cdot21+1958}{1980\cdot1979-1978\cdot1979}\\ =\frac{1978\cdot1979+\left(1979+1\right)\cdot21+1958}{1979\left(1980-1978\right)}\\ =\frac{1978\cdot1979+1979\cdot21+\left(21+1958\right)}{1979\cdot2}\\ =\frac{1978\cdot1979+1979\cdot21+1979}{1979\cdot2}\\ =\frac{1979\left(1978+21+1\right)}{1979\cdot2}\\ =\frac{2000}{2}\\ =1000\)
quá dễ