Especially recommended for advanced GCSE, a/as level and higher Replaces the old Casio fx-991es Plus 552 mathematical functions Solar powered with battery backup From the manufacturer Casio fx-991EX Advanced Scientific Calculator The Casio fx-991EX is Casios most advanced scientific calculator with 552 mathematical functions. Approved for Key stages 3, 4 and 5, recommended for Advanced GCSE, A/AS level and Highers. Allowed in every UK exam where a calculator can be used. The large Natural Textbook Display (Natural-V.P.A.M.) shows mathematical expressions like roots and fractions as they appear in your textbooks which increases comprehension because results are easier to understand. Read more The UKs best-selling Advanced Scientific calculator.