Codes (Shape Codes)

In Code questions, each shape (or picture) has been assigned a code made up of letters or symbols. Your job is to crack the code — work out what each letter means — and then apply it to a new shape.

This is like being a detective! You need to compare shapes and their codes to figure out which letter represents which property.

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How Code Questions Work

You are given some shapes with their codes, like this:

Shape 1: Large black circle      → Code: A X
Shape 2: Small black circle      → Code: B X
Shape 3: Large white circle      → Code: A Y
Shape 4: Small white square      → Code: B Y Z

Then you are asked: "What is the code for a Large black square?"

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The Strategy: Compare and Eliminate

The key to code questions is comparing two shapes that differ in only one property. If two shapes have almost the same code but one letter is different, that letter must represent the property that changed.

Step-by-Step Method

Step 1: Find two shapes that are almost the same but differ in ONE property.

Step 2: Look at their codes. Find the letter that is different.

Step 3: That letter = that property.

Step 4: Repeat until you have decoded all the letters.

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Worked Example 1

Shape 1: Large black circle      → Code: P R
Shape 2: Small black circle      → Code: Q R
Shape 3: Large white circle      → Code: P S

Question: What is the code for a Small white circle?

Step 1: Compare Shape 1 and Shape 2.

• Shape 1: Large black circle → P R
• Shape 2: Small black circle → Q R

Both are black circles. The only difference is size: Large vs Small. The codes differ by one letter: P vs Q.

So: P = Large, Q = Small.

Step 2: Compare Shape 1 and Shape 3.

• Shape 1: Large black circle → P R
• Shape 2: Large white circle → P S

Both are large circles. The only difference is colour: Black vs White. The codes differ by one letter: R vs S.

So: R = Black, S = White.

Step 3: We also know that circle is not coded (since all three shapes are circles and there is no common extra letter beyond what we have decoded). Or perhaps "circle" is implied.

Step 4: Build the code for Small white circle.

• Small = Q
• White = S

Answer: Q S.

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Worked Example 2

Shape 1: Large black triangle    → Code: A C E
Shape 2: Large white triangle    → Code: A D E
Shape 3: Small black triangle    → Code: B C E
Shape 4: Large black circle      → Code: A C F

Question: What is the code for a Small white circle?

Compare Shape 1 and Shape 2 (Large black triangle vs Large white triangle):

• Codes: A C E vs A D E
• Difference: C vs D — this must be the colour code.
• C = Black, D = White.

Compare Shape 1 and Shape 3 (Large black triangle vs Small black triangle):

• Codes: A C E vs B C E
• Difference: A vs B — this must be the size code.
• A = Large, B = Small.

Compare Shape 1 and Shape 4 (Large black triangle vs Large black circle):

• Codes: A C E vs A C F
• Difference: E vs F — this must be the shape code.
• E = Triangle, F = Circle.

Build the code for Small white circle:

• Small = B
• White = D
• Circle = F