$\frac{2^{2} }{3.5}$ +$\frac{2^{2} }{5.7}$ +$\frac{2^{2} }{7.9}$ +...+$\frac{2^{2} }{97.99}$
=2.($\frac{2}{3.5}$ +$\frac{2}{5.7}$ +$\frac{2}{7.9}$ +...+$\frac{2}{97.99}$ )
=2.($\frac{1}{3}$ -$\frac{1}{5}$ +$\frac{1}{5}$ -$\frac{1}{7}$ +$\frac{1}{7}$ -$\frac{1}{9}$ +...+$\frac{1}{97}$ -$\frac{1}{99}$ )
=2.($\frac{1}{3}$ -$\frac{1}{99}$ )
=2.$\frac{33}{99}$ -$\frac{1}{99}$ )
=2.$\frac{32}{99}$
=$\frac{64}{99}$ .
