Ta có:
$C = \dfrac{100^{16} + 1}{100^{17} +1}$
$⇒ 100C = \dfrac{100^{17} + 100}{100^{17} +1} = 1 + \dfrac{99}{100^{17}+1}$
$D = \dfrac{100^{15} + 1}{100^{16} +1}$
$⇒ 100C = \dfrac{100^{16} + 100}{100^{16} +1} = 1 + \dfrac{99}{100^{16}+1}$
Mà $\dfrac{99}{100^{17}+1} < \dfrac{99}{100^{16}+1}$ $⇒$ $100C < 100D$
$⇒$ $C<D$