A trader bought 100 tubers at 5 for N350.00. She sold them in sets of 4 for N290.00. Find her gain percent.

A man's initial salary is N540.00 a month and increases after each period of six months by N36.00. Find his salary in the eight month of the third year.

At what rate would a sum of N100.00 deposited for 5 years raise an interest of N7.50?

Musa borrows N10.00 at 2% per month simple interest and repays N8.00 after 4 months. How much does he still owe?

 A trader paid import duty of 38 kobo in the naira on the cost of an engine. If a total of #22,800.00 was paid as import duty, calculate the cost of the engine.