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Curious math.com: Math Is an Attitude
This site offers numbers tricks to help multiply and divide large numbers mentally. There are also tricks for powers and roots of numbers.
Topmarks Online
Topmarks: Daily 10
Daily 10 has maths questions on a range of maths concepts: addition, subtraction, ordering, partitioning, digit values, rounding, multiplication, division, doubles, halves and fractions. Great starter or plenary activity. Useful for...
University of Waterloo (Canada)
University of Waterloo: Powerama 6 D
In this game, you simply divide the two numbers. All exercises are division by 10, 100, 1000, or 10,000, so students can learn quick mental methods of division by powers of ten. The game presents 100 exercises, so students get plenty of...
Topmarks Online
Topmarks: Loop Cards
Fantastic for improving your mental maths. Similar to dominoes, complete the loop against the clock while practicing addition, subtraction, multiplication, and division.
K-5 Math Teaching Resources
K 5 Math Teaching Resources: Estimate the Quotient [Pdf]
This activitiy asks students to randomly select a one-digit divisor and a three-digit dividend and estimate the quotient mentally. Students must then explain why they believe their estimate is accurate.