Smart Maths Tricks for Class 8 CBSE Students

Why You Need Smart Maths Tricks for Class 8 CBSE

Class 8 CBSE maths is where things get serious. Algebra gets harder. Geometry gets trickier. And if you're still solving everything the long way, you're going to waste precious time during exams.

These aren't shortcuts or tricks that replace understanding. They're methods that save time after you know the concept. Use them in exams. Use them in practice. Stop doing math the hard way when a simpler path exists.

Vedic Maths Tricks That Actually Work

Multiplying by 11 Takes 3 Seconds

Forget the long multiplication method. Here's the actual fast way.

For two-digit numbers: Split the digits. Add them together. Put the sum in the middle.

Example: 47 × 11

• Split 4 and 7
• 4 + 7 = 11
• Put 11 between 4 and 7
• Answer: 517

What if the sum is 10 or more? Add the tens digit to the left number.

Example: 78 × 11

• 7 and 8
• 7 + 8 = 15
• Keep 7, keep 8, put 5 in middle
• 7 + 1 (carry) = 8
• Answer: 858

Squaring Numbers Ending in 5

This trick works every time. No exceptions.

Rule: Take the digit before 5, multiply it by the next number, append 25.

35² = ?

• Digits before 5: 3
• Next number: 4
• 3 × 4 = 12
• Append 25
• Answer: 1225

85² = ?

• Digits before 5: 8
• Next number: 9
• 8 × 9 = 72
• Append 25
• Answer: 7225

This works for any number ending in 5. Practice it until it's automatic.

Percentage Tricks for Class 8 Algebra

Finding Percentages Without a Calculator

The key insight: 10% of any number is just divide by 10. Build from there.

What is 35% of 240?

• 10% of 240 = 24
• 30% = 24 × 3 = 72
• 5% = 12
• 35% = 72 + 12 = 84

Break percentages into multiples of 10 and 5. It's always easier than multiplying by decimal fractions.

Reverse Percentages

If a price increases by 20% to become ₹600, what was the original price?

• After 20% increase: 120% of original = 600
• 1% of original = 600 ÷ 120 = 5
• Original = 5 × 100 = ₹500

Or faster: Original = New Price × 100 ÷ (100 + Percentage Increase)

Algebra Shortcuts for Linear Equations

Solving Equations Faster

For equations like 3x + 7 = 22, don't rewrite the entire equation. Just isolate mentally.

3x + 7 = 22

• Move 7 to the other side: 3x = 22 - 7
• 3x = 15
• x = 15 ÷ 3
• x = 5

The only rule: whatever you do to one side, do to the other. That's it. No need to rewrite each step if you can do it mentally.

Checking Your Answer Without Re-solving

Always substitute your answer back into the original equation. Takes 5 seconds. Catches most mistakes. Do it.

Cube and Cube Root Tricks

Perfect Cubes You Must Memorize

For Class 8, memorize cubes of 1 through 10. You'll need them constantly.

Cube roots of these numbers are just the reverse. √³64 = 4. √³125 = 5. No calculation needed if you know your cubes.

Divisibility Rules That Save Time

Use these to simplify fractions and find factors without long division.

• Divisible by 2: Last digit is even
• Divisible by 3: Sum of digits is divisible by 3
• Divisible by 4: Last two digits form a number divisible by 4
• Divisible by 5: Ends in 0 or 5
• Divisible by 6: Divisible by both 2 and 3
• Divisible by 9: Sum of digits is divisible by 9

Example: Is 432 divisible by 3?

4 + 3 + 2 = 9. 9 is divisible by 3. So 432 is divisible by 3. Answer: 144.

Geometry Shortcuts for Class 8

Finding Diagonals in Quadrilaterals

In a polygon with n sides, number of diagonals = n(n-3)/2

For a hexagon (n=6): 6(6-3)/2 = 6×3/2 = 9 diagonals

For a pentagon (n=5): 5(5-3)/2 = 5×2/2 = 5 diagonals

No drawing required. Just apply the formula.

Sum of Interior Angles

For any polygon with n sides: Sum = (n-2) × 180°

Quadrilateral: (4-2) × 180 = 360° ✓

Triangle: (3-2) × 180 = 180° ✓

Octagon: (8-2) × 180 = 1080°

Comparing Traditional vs Smart Approach

How to Actually Use These Tricks

Reading tricks doesn't make you faster. Practicing them makes you faster.

1. Pick one trick. Start with multiplying by 11. It's the easiest to learn.
2. Practice it for 15 minutes. Generate random two-digit numbers. Multiply by 11 in your head.
3. Test yourself. Time how fast you can solve 10 problems with the trick versus the traditional method.
4. Move to the next trick. Once one is automatic, learn another.
5. Mix them during revision. Use whichever trick fits the problem.

Don't try to learn everything in one day. Master one or two tricks per week. By your next exam, you'll be noticeably faster.

Common Mistakes That Kill Your Speed

• Using tricks before understanding the concept. These tricks supplement knowledge. They don't replace it. Know why 10% works before you use it.
• Overcomplicating simple problems. Sometimes the traditional method is faster. Don't force a trick where it doesn't fit.
• Not memorizing perfect squares and cubes. You lose more time calculating than you save with tricks. Memorize 1-20 squares and 1-10 cubes.
• Writing every step. Do more in your head. Only write what you need to avoid mistakes.

What to Memorize Right Now

If you memorize nothing else from this article, memorize these:

• Squares of 1-20
• Cubes of 1-10
• Divisibility rules for 2, 3, 4, 5, 6, 9
• Angle sum formula: (n-2) × 180°
• Diagonal formula: n(n-3)/2

That's the bare minimum. The rest of these tricks are useless without the foundation memorized.

Where These Tricks Actually Matter

These tricks matter most during:

• Board exams — Every minute counts. Save time on easy calculations so you have more for hard questions.
• Competitive exams — Speed matters. Students who know these tricks finish before others.
• Daily homework — Less time on math means more time for other subjects.

Stop treating math like a chore. Learn the patterns. Use the shortcuts. Your future self will thank you when you're not wasting 20 minutes on calculations that should take 5.