Divisibility Rules Uncovered: Detective Work
Year 5 Mathematics Become a Divisibility Detective! Discover the secrets of numbers
Learning Objectives - What Will You Discover?
Understand divisibility rules for 2, 3, 5, 10, and 11 Apply these rules to quickly identify divisible numbers Use divisibility shortcuts in mental calculations Solve number mysteries like a true detective!
Detective Training: The Sweet Mystery
You have 24 sweets to share equally among friends Can you share them equally among 5 friends? What about 4 friends? Or 3 friends? This is where divisibility helps us solve the mystery!
Detective Tool #1: Rule of 2
A number is divisible by 2 if the last digit is EVEN Even digits: 0, 2, 4, 6, 8 Examples: 24 ✓, 67 ✗, 138 ✓ Quick test: Just look at the last digit!
Detective Tool #2: Rule of 3
A number is divisible by 3 if the SUM of its digits is divisible by 3 Example: 123 → 1+2+3 = 6, and 6÷3 = 2 ✓ Example: 125 → 1+2+5 = 8, and 8÷3 = not whole ✗ Add up all the digits, then check if that total can be divided by 3
Detective Tools #3 & #4: Rules of 5 and 10
Rule of 5: Last digit must be 0 or 5 Examples: 45 ✓, 120 ✓, 67 ✗ Rule of 10: Last digit must be 0 Examples: 340 ✓, 125 ✗, 1000 ✓
Detective Tool #5: The Tricky Rule of 11
Take the sum of digits in odd positions (1st, 3rd, 5th...) Take the sum of digits in even positions (2nd, 4th, 6th...) Subtract the second sum from the first If the result is 0 or divisible by 11, the number is divisible by 11!
Divisibility Stations: Detective Training Ground
Station 1: Rule of 2 - Spot the even endings Station 2: Rule of 3 - Add those digits! Station 3: Rule of 5 - Find 0s and 5s Station 4: Rule of 10 - Zero endings only Station 5: Rule of 11 - The ultimate challenge 4 minutes per station, then rotate!
Divisibility Relay: Detective Championship
Teams compete to identify divisibility rules One team member runs to the board State which rules apply to the given number Explain your reasoning to earn points Every detective gets a turn!
Detective Debrief: Assessment & Reflection
Quick Quiz: Test your detective skills on mystery numbers Which divisibility rules can you remember? How do these rules help us in everyday maths? When might you use these detective skills in real life?