Hello everyone i purchase Casio FX-991ES Plus Scientific Calculator during my engineering days and recently i purchase new Casio calculator. Really it’s a best calculator for quickly solving any numerical or mathematics problems without any lengthy calculation using by pen on paper, it has very special and unique features available, easily you can solve matrices, determinant as well as complex numbers, integral & differential calculus by using this, Also Casio one of the best brand in the field of electronic market. I recommended this one all professional students specially for engineering student. Thank you.