Since they were first introduced over 30 years-ago, hand-held calculators have become so universally common and relied-upon it sometimes seems we've lost the ability to perform simple math calculations without them--which is a problem when yours has gotten lost or mysteriously walks-off. Here's a great solution: a calculator so large it's almost impossible to lose or misplace with the features we've come to depend on. Dependable dual-power operation from miniature solar panel that absorbs energy from any light source and an internal battery that never needs replacing.