MENTAL MATHS STRATEGIES

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By ABEL ASIEDU

​MENTAL MATHS STRATEGIES

• It's like a brain superpower!

• Helps in games, shopping, and sharing treats.

• Rule: Practice daily to get faster.

Why Mental maths?

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• Rule 1: Break into hundreds, tens, ones. Add parts, combine.

• Rule 2: Bridge to 10 or 100, then adjust.

• Rule 3: Round and fix.

• Rule 4: Use doubles or easy facts.

• Always estimate first!

Addition rules

Bridging

Addition Example 1

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• Problem: 123 + 456

• Step: Break – (100+400) + (20+50) + (3+6) = 500 + 70 + 9 = 579

• Estimate: 100+500=600 (close!).

Addition Example 2

• Problem: 198 + 25

• Step: Bridge – 198 + 2 = 200, then +23 = 223

• Like jumping over a river!

Subtraction Rules

Rules

• Rule 1: Break and subtract parts (borrow if needed).

• Rule 2: Bridge down to 10/100.

• Rule 3: Round the subtract number, fix.

• Rule 4: Count up from smaller to bigger.

• Estimate to check.

EXAMPLE 3

• Problem: 579 - 123

• Step: Break – (500-100) + (70-20) + (9-3) = 400 + 50 + 6 = 456

EXAMPLE 4

• Problem: 500 - 198

• Step: Round – 500 - 200 = 300, add back 2 = 302

Multiple Choice

267+189

• 456

• 546

• 465

• 654

Multiple Choice

267+189

• 456

• 546

• 465

• 654

Fill in the Blank

256+129

Fill in the Blank

350+625

Fill in the Blank

670+720

FRACTIONS RULES

• Rule 1: Same denominator only.

• Rule 2: Add/subtract tops, keep bottom.

• Rule 3: If over 1, make mixed number.

• Rule 4: Estimate (close to 0, 1/2, 1?).

EXAMPLE 5

• Problem: 2/5 + 1/5

• Step: (2+1)/5 = 3/5

Fill in the Blank

2/7+3/7

/

Fill in the Blank

1/6+2/6

/

Fill in the Blank

4/9+2/9

/

COMPARING FRACTIONS RULES

• Rule 1: Make same denominator.

• Rule 2: Compare tops.

• Rule 3: Picture it (half vs. third).

• Rule 4: Equivalent = same value (e.g., 1/2=2/4).

Multiple Choice

Which is larger? 2/4 OR 1/2

• 2/4

• 1/2

• Same

• None

Multiple Choice

Which is larger? 1/2 OR 3/4

• 1/2

• 3/4

• Same

• None

Multiplication Rules

• Rule 1: Use times tables (1-10).

• Rule 2: Break big number, multiply parts.

• Rule 3: Double for x2, x4, x8.

• Rule 4: x5 = x10 then halve.

• Rule 5: Estimate.

EXAMPLE 6

• Problem: 123 x 3

• Step: 100x3=300 + 20x3=60 + 3x3=9 = 369

Fill in the Blank

223*2

Fill in the Blank

45*2

Fill in the Blank

450*5

Fill in the Blank

234*3

YOU'RE A MATH HEROINE

CONGRATULATIONS AVA