Môn Toán Lớp 6: `12/1.5 + 12/5.9 + 12/9.23 + … + 12/97.101`

$\dfrac{12}{1.5}$ + $\dfrac{12}{5.9}$ + $\dfrac{12}{9.13}$ +…+ $\dfrac{12}{97.101}$

= 3 . ($\dfrac{4}{1.5}$ + $\dfrac{4}{5.9}$ + $\dfrac{4}{9.13}$ +…+ $\dfrac{4}{97.101}$)

= 3 . ($\dfrac{1}{1}$ – $\dfrac{1}{5}$ + $\dfrac{1}{5}$ – $\dfrac{1}{9}$ + $\dfrac{1}{9}$ – $\dfrac{1}{13}$ +…+ $\dfrac{1}{97}$ – $\dfrac{1}{101}$)

= 3 . ($\dfrac{1}{1}$ – $\dfrac{1}{101}$)

= 3 . $\dfrac{100}{101}$

= $\dfrac{300}{101}$