IOS 7.0 or later, iPhone/iPad/iPod Touch, Android 4.1 or later, free
SALMAN KHAN BELIEVES that learning should be free to all, which is why he started educational website the Khan Academy. Now, the redesigned app allows you to learn on the go. It provides access to over 10,000 videos and explanations at all levels of experience, with science and maths being two core disciplines covered. There are quizzes to help solidify the lessons, plus 150,000 maths exercises for those who fancy giving their number-crunching skills a workout.