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🔀 Strategies

Interleaving

Stop practising one topic at a time. Mix them up. Here's why — and how.

Here's a revision mistake almost everyone makes:

You sit down to revise trigonometry. You do 15 trigonometry problems. You get most of them right. You feel confident. You move on to the next topic.

Then in the exam, you see a triangle problem and think: "Wait... is this Pythagoras? Trigonometry? Similar triangles? Sine rule?"

You freeze. The problem isn't that you can't do trigonometry. The problem is you can't recognise when to use it.

This is why interleaving is essential.

What Is Interleaving?

Blocked practice: Doing lots of the same type of problem in a row

  • 15 Pythagoras questions, then 15 area questions, then 15 percentage questions

Interleaved practice: Mixing different types of problems together

  • Pythagoras, then area, then percentage, then Pythagoras again, then something else entirely

Both approaches use the same problems. The only difference is the order.

And that small change makes a dramatic difference to your exam results.

The Research Is Striking

In a study with school students, researchers compared blocked vs interleaved maths practice:

Condition Score During Practice Score on Test (1 Day Later)
Blocked 89% 38%
Interleaved 63% 77%

Read that again.

Students who used blocked practice scored higher during practice but much lower on the actual test.

Students who used interleaved practice struggled more during practice but scored nearly twice as high when it counted.

This is one of the most important findings in learning science — and most students do the opposite.

Why Interleaving Works

1. It Forces You to Identify Problem Types

With blocked practice, you know what method to use before you even read the question. "I'm doing the Pythagoras section, so I'll use Pythagoras."

With interleaving, you have to figure out what each problem is actually asking. Is this:

  • Pythagoras?
  • Trigonometry?
  • Similar triangles?
  • Something else?

This discrimination skill is exactly what you need in an exam.

2. It Mimics Exam Conditions

Your GCSE maths paper doesn't group questions by topic. Question 5 might be algebra, Question 6 geometry, Question 7 statistics.

If you've only ever practised in blocks, you've never practised the actual skill of switching between topics.

3. It Creates Desirable Difficulty

Interleaving feels harder. You make more mistakes during practice. But that struggle is creating stronger learning.

Easy practice = weak learning. Difficult practice = strong learning.

4. It Helps You See Connections

When you mix topics together, you start noticing connections between them:

  • "Oh, this area problem also needs Pythagoras to find the height"
  • "This probability question is really just a fractions question"
  • "I need to rearrange this formula before I can substitute"

These connections are crucial for the harder exam questions that combine multiple topics.

How to Interleave Your Maths Practice

Method 1: The Mixed Problem Set

Create (or find) problem sets that mix different topics:

Example set:

  1. Calculate $\frac{3}{4} + \frac{2}{5}$
  2. Find the gradient of the line through (2, 5) and (6, 13)
  3. Expand and simplify $(x + 3)(x - 7)$
  4. A shop reduces prices by 15%. A jacket was £80. Find the new price.
  5. Find angle $x$ in a right-angled triangle with opposite = 8, adjacent = 15
  6. Solve $3x + 7 = 22$
  7. Find the area of a circle with radius 5cm
  8. Simplify $\sqrt{72}$

The key: Each problem requires you to first identify what it's asking, then select the right approach.

Method 2: Shuffle Your Flashcards

If you're using flashcards, shuffle them thoroughly so formula cards from different topics are mixed together.

Don't sort by topic. Don't work through one topic at a time. Randomise.

Method 3: Past Paper Questions (Rearranged)

Take questions from multiple past papers and mix them up:

  • 5 random questions from Paper 1
  • 5 random questions from Paper 2
  • 5 random questions from a different year

You can find random question generators online, or just pick questions with your eyes closed.

Method 4: Topic Rotation Sessions

Structure your revision sessions to rotate between topics:

30-minute session:

  • 0-10 mins: Algebra problems
  • 10-20 mins: Geometry problems
  • 20-30 mins: Mixed problems including algebra and geometry

The mixed section at the end is crucial — that's where the real interleaving happens.

What to Interleave

Interleaving is most powerful when you mix topics that are related but different:

High-Value Interleaving Combinations

Triangles:

  • Pythagoras, Trigonometry (SOHCAHTOA), Sine rule, Cosine rule, Similar triangles, Area of triangles

Algebra solving:

  • Linear equations, Quadratic equations, Simultaneous equations, Inequalities, Rearranging formulas

Percentages and proportion:

  • Percentage increase/decrease, Reverse percentages, Compound interest, Ratio, Direct/inverse proportion

Area and perimeter:

  • Rectangles, Triangles, Circles, Trapeziums, Compound shapes, Surface area

Data and graphs:

  • Mean/median/mode, Cumulative frequency, Box plots, Histograms, Scatter graphs

Mixing similar topics forces you to discriminate between them — which is exactly what the exam will require.

The Interleaving Trap

Warning: Interleaving only works if you already have a basic understanding of each topic.

If you've never learned quadratic equations, mixing them with other topics won't help — you'll just fail every quadratic question.

The sequence should be:

  1. Learn the topic (blocked practice is fine here)
  2. Consolidate with a few more blocked problems
  3. Interleave with other topics you know

Don't interleave too early. But don't skip it either.

"But It Feels Like I'm Doing Worse!"

Yes. That's the point.

Interleaving will feel harder. You'll get more wrong during practice. You might feel like you're going backwards.

This is called the illusion of learning: blocked practice feels effective because you get answers right. Interleaved practice feels ineffective because you struggle.

But what matters is the exam, not the practice session.

Would you rather:

  • Feel good during practice, struggle in the exam?
  • Struggle during practice, succeed in the exam?

The discomfort during interleaved practice is the sign that learning is happening.

Practical Interleaving Schedule

Here's how to build interleaving into your week:

Daily (20-30 mins)

  • Start with 5 mixed questions from previous topics (retrieval practice)
  • Focus time on one topic (learning/consolidation)
  • End with 5 mixed questions including today's topic

Weekly (1-2 hours)

  • One longer session of entirely mixed practice
  • Include topics from the past month
  • Don't check what topic each question is — just solve it

Monthly

  • Full past paper (which is naturally interleaved)
  • Review which topics you struggled to identify, not just which you got wrong

Interleaving + Spacing + Retrieval

The three strategies work best together:

Strategy What It Does
Spacing Ensures you revisit topics at the right intervals
Retrieval Ensures you're actually testing yourself, not just reading
Interleaving Ensures you can identify problems, not just solve them

A perfect revision session:

  1. Retrieval: Start by testing yourself on previous material
  2. Interleaving: Mix different topics together
  3. Spacing: Make sure you're returning to topics at increasing intervals

Quick Start

Here's how to start interleaving today:

  1. Pick three topics you've already learned
  2. Find (or write) 4 questions from each topic
  3. Number them 1-12 randomly — don't group by topic
  4. Do all 12 questions in order, deciding which topic each one is before solving
  5. Check your answers
  6. Note which problems you couldn't identify (these need more practice)

It will feel harder than normal. That means it's working.

The bottom line: Your exam is interleaved. Your revision should be too.

Ready to put it all together?