Number Sense Tricks

• Squares and powers (reference)
• Pythagorean triples (reference)
• Trigonometry (reference)
• Unit conversions (reference)
• Multiplying by 11
• Difference of squares
• Sums of series
• X^2/Y mixed number trick
• Mixed number multiplication
• Squaring numbers ending in 5
• Nineties trick
• Positive integral divisors
• Sum of squares
• Base conversion
• Sevens estimation problems