tính tổng các phân số sau:S=5/1.6+5/6/11+5/11.16+5/16.21+5/21.26

Đáp án:

S = $\frac{5}{1.6}$ + $\frac{5}{6.11}$ + $\frac{5}{11.16}$ + $\frac{5}{16.21}$ + $\frac{5}{21.26}$

S = $\frac{1.5}{1.6}$ + $\frac{1.5}{6.11}$ + $\frac{1.5}{11.16}$ + $\frac{1.5}{16.21}$ + $\frac{1.5}{21.26}$

S = 1 - $\frac{1}{6}$ - $\frac{1}{6}$ + $\frac{1}{11}$ - $\frac{1}{11}$ + $\frac{1}{16}$ - $\frac{1}{16}$ + $\frac{1}{21}$ - $\frac{1}{21}$ + $\frac{1}{26}$ - $\frac{1}{26}$

S = 1 - $\frac{1}{26}$

S = $\frac{25}{26}$