Nils invests his savings in an account that pays $6\%$ interest compounded half yearly. If he puts $\$2300$ into his account and leaves it there for two years, how much money will he have at the end of the period?

A colony of bacteria grows by 5% every hour. How long does it take for the colony to double in size?

Find the actual profit and percentage profit of the following:

Cost price $\$20$, Selling price $\$25$

Find the actual profit and percentage profit of the following:

Cost price $\$500$, Selling price $\$550$

Find the actual profit and percentage profit of the following:

Cost price $\$1.50$, Selling price $\$1.80$

Find the actual profit and percentage profit of the following:

Cost price $30$ cents, Selling price $35$ cents

Find the percentage loss of the following:

Cost price $\$400$, Selling price $\$300$