Keep an eye on my maths blog as I will be adding maths websites as the year continues. Please also ensure there is adult supervision when online as although the websites have been tried & tested, unsuitable advertisements could still pop-up.
https://www.khanacademy.org/ Khan Academy is a free online (American) maths resource. Can be used to revise topics or challenge oneself. 3rd grade would be mainly revision. 4th/5th grade to revise and challenge.
https://mathsframe.co.uk/en/resources/category/22/most-popular (lots of free & tablet friendly games, careful with pop-up ads)
Interactive online games and activities to make learning tables fun!
https://www.topmarks.co.uk/maths-games/7-11-years/times-tables (lots of tablet-friendly games)
Problem solving game involving time;
Games to explore fractions;
https://www.topmarks.co.uk/maths-games/7-11-years/fractions-and-decimals (tablet friendly games)
https://www.mathplayground.com/index_fractions.html (some tablet friendly activities)
Games/activities for decimals;
https://www.topmarks.co.uk/place-value/place-value-charts (tablet friendly)
Maths challenging puzzle activities (including sudukos & magic squares)
https://www.transum.org/Software/Puzzles/ (tablet friendly puzzles)
https://www.mathwarehouse.com/riddles/math-riddles.php (challenging riddles)
Activities for division practice;
http://www.hoodamath.com/games/demolitiondivision.html (some tablet friendly activities)
http://www.novelgames.com/en/quickmath/ (tablet friendly but watch for pop-up ads)