Online Activities for 2nd - 4th Classes
Khan Academy - Area (Third Grade): Watch the videos and then answer the practice questions. You can also register for a free Khan Academy account to record your progress and explore other topics/grades.
Happy Numbers Third Grade: Pupils could start the activities in Module 4, Topics A, B and D. When completed they could move on to all the topics in Grade 4, Module 2, Topic A.
Area & Perimeter: Tool from Toy Theater, for exploring and creating shapes with various areas. Another similar tool is this one from Maths Frame
Area: a selection of games from ixl.com. You can do a number of free quizzes each day without having a subscription. Choose your class level.