Elemen Try Math

The term for such tricks, observations, or shortcuts in math is “divisibility rules” or more generally “mathematical heuristics” (rules of thumb that simplify problem-solving). These are patterns or strategies that help students quickly determine properties of numbers without performing full calculations.

Other Examples for Elementary Math Students:

1. Divisibility Rules:

• Divisibility by 2: A number is divisible by 2 if its last digit is even (0, 2, 4, 6, 8).

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• Divisibility by 5: A number is divisible by 5 if it ends in 0 or 5.

• Divisibility by 9: A number is divisible by 9 if the sum of its digits is a multiple of 9 (similar to the rule for 3).

2. Multiplication Shortcuts:

• Multiplying by 5: Multiply by 10 and then divide by 2. Example: .

• Multiplying by 9: Use fingers—hold out ten fingers, lower the finger at the number you’re multiplying by 9, and the left-hand side shows tens, the right-hand side shows ones. Example: → three fingers left, six fingers right → 36.

3. Squaring Tricks:

• Squaring numbers ending in 5: If a number ends in 5, multiply the first digit by itself plus 1, then append 25. Example: → 12, then append 25 → 1225.

4. Adding & Subtracting Quickly:

• Compensation Strategy: If adding 29 + 47, round 29 to 30 (add 1), add 30 + 47 = 77, then subtract the extra 1 → 76.

• Using 10s for Subtraction: If subtracting 83 – 29, think 83 – 30 = 53, then add back 1 → 54.

5. The Rule of 11 for Checking Numbers:

• Take alternating sums of the digits and find the difference. If it’s a multiple of 11, the number is divisible by 11. Example: 2728 → (2+2) – (7+8) = 4 – 15 = -11 (divisible by 11).

These simple patterns make math fun and intuitive for kids! Want more?
50 Math Tricks That Will Change Your Life: Mentally Solve the Impossible in Seconds

50 amazing Math Tricks on Amazon

The term for such tricks, observations, or shortcuts in math is “divisibility rules” or more generally “mathematical heuristics” (rules of thumb that simplify problem-solving). These are patterns or strategies that help students quickly determine properties of numbers without performing full calculations.

Other Examples for Elementary Math Students:

1. Divisibility Rules:

• Divisibility by 2: A number is divisible by 2 if its last digit is even (0, 2, 4, 6, 8).

quote”>

• Divisibility by 5: A number is divisible by 5 if it ends in 0 or 5.

• Divisibility by 9: A number is divisible by 9 if the sum of its digits is a multiple of 9 (similar to the rule for 3).

2. Multiplication Shortcuts:

• Multiplying by 5: Multiply by 10 and then divide by 2. Example: .

• Multiplying by 9: Use fingers—hold out ten fingers, lower the finger at the number you’re multiplying by 9, and the left-hand side shows tens, the right-hand side shows ones. Example: → three fingers left, six fingers right → 36.

3. Squaring Tricks:

• Squaring numbers ending in 5: If a number ends in 5, multiply the first digit by itself plus 1, then append 25. Example: → 12, then append 25 → 1225.

4. Adding & Subtracting Quickly:

• Compensation Strategy: If adding 29 + 47, round 29 to 30 (add 1), add 30 + 47 = 77, then subtract the extra 1 → 76.

• Using 10s for Subtraction: If subtracting 83 – 29, think 83 – 30 = 53, then add back 1 → 54.

5. The Rule of 11 for Checking Numbers:

• Take alternating sums of the digits and find the difference. If it’s a multiple of 11, the number is divisible by 11. Example: 2728 → (2+2) – (7+8) = 4 – 15 = -11 (divisible by 11).

These simple patterns make math fun and intuitive for kids! Want more?
50 Math Tricks That Will Change Your Life: Mentally Solve the Impossible in Seconds

50 amazing Math Tricks on Amazon

FYI Asked ChatGPT

Did you learn in 3rd grade that any number whose individual digits add up to 3 , 6 or 9 are divisible by 3?

What term is used for such tricks, observations or short cuts ? AND what other examples can you suggest for elementary math students ?

ANSWER

The term for such tricks, observations, or shortcuts in math is “divisibility rules” or more generally “mathematical heuristics” (rules of thumb that simplify problem-solving). These are patterns or strategies that help students quickly determine properties of numbers without performing full calculations.

Other Examples for Elementary Math Students:

1. Divisibility Rules:

• Divisibility by 2: A number is divisible by 2 if its last digit is even (0, 2, 4, 6, 8).

quote”>

• Divisibility by 5: A number is divisible by 5 if it ends in 0 or 5.

• Divisibility by 9: A number is divisible by 9 if the sum of its digits is a multiple of 9 (similar to the rule for 3).

2. Multiplication Shortcuts:

• Multiplying by 5: Multiply by 10 and then divide by 2. Example: .

• Multiplying by 9: Use fingers—hold out ten fingers, lower the finger at the number you’re multiplying by 9, and the left-hand side shows tens, the right-hand side shows ones. Example: → three fingers left, six fingers right → 36.

3. Squaring Tricks:

• Squaring numbers ending in 5: If a number ends in 5, multiply the first digit by itself plus 1, then append 25. Example: → 12, then append 25 → 1225.

4. Adding & Subtracting Quickly:

• Compensation Strategy: If adding 29 + 47, round 29 to 30 (add 1), add 30 + 47 = 77, then subtract the extra 1 → 76.

• Using 10s for Subtraction: If subtracting 83 – 29, think 83 – 30 = 53, then add back 1 → 54.

5. The Rule of 11 for Checking Numbers:

• Take alternating sums of the digits and find the difference. If it’s a multiple of 11, the number is divisible by 11. Example: 2728 → (2+2) – (7+8) = 4 – 15 = -11 (divisible by 11).

These simple patterns make math fun and intuitive for kids! Want more?
50 Math Tricks That Will Change Your Life: Mentally Solve the Impossible in Seconds

50 amazing Math Tricks on Amazon