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IMO Maths Tricks

by admin · October 19, 2026

LEARN • PRACTISE • ACHIEVE

The smart practice guide • Classes 3, 4 & 5

Small tricks.
Big “I got it!”
moments.

Three useful IMO maths tricks to help young problem-solvers spot patterns, calculate faster and build confidence.

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TODAY’S PRACTICE. TOMORROW’S PROGRESS.

Olympiad maths rewards a curious mind. Sometimes, a small change in how you look at a question makes the calculation much easier. Here are three IMO maths tricks—one each for Classes 3, 4 and 5—with worked examples and a quick challenge.

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Class 3 • Mental maths

Make a round number

Adding 9, 19 or 29? First add 10, 20 or 30, then subtract 1. Numbers close to multiples of 10 are your clue!

Let’s solve it

Find 47 + 29. Since 29 is one less than 30:

47 + 30 − 1 = 76

Add 30 to get 77. Take away the extra 1. Done!

💡 Why it works: Using 30 instead of 29 adds 1 extra. Subtracting 1 keeps the total correct.

Where it helps: Mental maths, addition puzzles and word problems involving totals.

✏️ Your turn: What is 68 + 19?

Answer: 68 + 20 − 1 = 87

While solving IMO Previous Year Papers Class 3, look for numbers close to multiples of 10 and try this method.

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Class 4 • Number patterns

Pair numbers to add faster

A long addition can become a short multiplication. Pair the smallest number with the largest, then work your way inwards.

Let’s solve it

Find the sum of the numbers from 1 to 20.

1 + 20 = 212 + 19 = 213 + 18 = 21

Continue the pattern: 10 pairs, each with a total of 21.

10 × 21 = 210

💡 Why it works: As one number increases by 1, its partner decreases by 1. Every pair keeps the same total.

Where it helps: Number series, counting problems and sums of consecutive numbers.

✏️ Your turn: Add the numbers from 11 to 20.

Pair 11 with 20, 12 with 19, and so on. There are 5 pairs of 31.
Answer: 5 × 31 = 155

🔎 Watch out: With an odd number of terms, one middle number remains. Add it separately.

Practise spotting these patterns in IMO Previous Year Papers Class 4.

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Class 5 • Visual reasoning

Count rectangles with line pairs

Counting shapes one by one can lead to missed rectangles. Instead, choose two vertical lines and two horizontal lines. These four lines form exactly one rectangle.

Let’s solve it

How many rectangles are in this complete grid?

3 columns × 2 rows
4 vertical boundary lines
3 horizontal boundary lines

Choose two vertical lines.
4 × 3 ÷ 2 = 6 pairs.
Choose two horizontal lines.
3 × 2 ÷ 2 = 3 pairs.
Multiply the choices.
Each vertical pair works with each horizontal pair.

6 × 3 = 18 rectangles

💡 Why divide by 2? Choosing line A then line B gives the same pair as choosing B then A. Dividing by 2 removes this double counting.

Where it helps: Figure-counting and visual reasoning questions.

✏️ Your turn: Count the rectangles in a 2-column, 2-row grid.

3 vertical lines give 3 pairs. 3 horizontal lines also give 3 pairs.
Answer: 3 × 3 = 9 rectangles

🔎 Remember: Squares count as rectangles unless excluded by the question. This method applies to a complete rectangular grid.

Use IMO Previous Year Papers Class 5 to practise spotting small rectangles, larger rectangles and combinations of cells.

Build a winner’s practice habit

Understand it. Try it. Make it stick.

A shortcut becomes useful when students understand why it works and when to use it. Start without a timer, check mistakes, then try similar questions under timed conditions.

Explore IMO Previous Year Papers for Classes 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Choose your child’s class and build a regular practice routine.

Class 1Class 2Class 3Class 4Class 5Class 6Class 7Class 8Class 9Class 10

Ready for your next “I got it!” moment?

With SOF Olympiad Trainer, combine Previous Year Papers with chapter-wise practice and mock tests to build accuracy, confidence and smarter problem-solving habits.

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LEARN THE METHOD. SPOT THE PATTERN. PRACTISE WITH PURPOSE.