Texas Instruments most widely used, durable low-cost school calculator. Bright, color-coded keyboard with easy-to-use hard plastic keys. Dual (Solar and Battery)-Operates in well-lit areas using solar cell. Operates in other light settings using battery. Percent key helps figure tips, taxes, and discounts. Change sign (+-) key allows entry of negative numbers Protective slide case included Appropriate for: Math Grades K-3 Texas Instrument's most widely used school calculator is available here in a Teacher Kit. It contains 10 Calculators, a poster and instructional materials.