SEAGReady
MeasurementP7 level26 questions in the full course

Find Missing DimensionsSEAG Practice Questions

Using known area, perimeter, or volume to work backwards and find a missing length, width, or height.

Where your child meets this in real life: Determining the width of a room given the floor area and length, or height of a box given volume

What your child needs to know

SEAGReady breaks find missing dimensions into 3 steps, taught in order so each skill builds on the last.

  1. 1

    From Rectangle Area

    Find a missing side of a rectangle when given the area and one side length

  2. 2

    From Rectangle Perimeter

    Find a missing side of a rectangle when given the perimeter and one side length

  3. 3

    From Cuboid Volume

    Find a missing dimension of a cuboid when given the volume and two other dimensions

Try these SEAG-style questions

Three free sample questions from our find missing dimensions course. Every question comes with a full explanation, and hints that guide without giving the answer away.

Question 1Confidence builder

Use the diagram to find the missing width.

A rectangle marked not to scale with 20 m² and one missing side.
Answer choices for question 1
Question 2Standard

Use the diagram to find the missing side length.

A rectangle marked not to scale with its full boundary highlighted and Perimeter = 32 cm.
Answer choices for question 2
Question 3Confidence builder

Use the diagram to find the missing height of the fish tank.

A fish tank marked not to scale with Volume = 60 cm³ and its height labelled with a question mark.
Answer choices for question 3

Try the lesson: From Rectangle Area

This is the exact interactive worked example your child sees in SEAGReady. Step through it and watch the method build up.

Ava is buying a rug for her bedroom. The rug has an area of 24 m² and is 6 m long.

What is the width of the rug?

24 ÷ 6 = ?

Recall the area formula
1

Area = length x width

Step 1 of 4

Prefer to read? See every step written out

Ava is buying a rug for her bedroom. The rug has an area of 24 m² and is 6 m long.

What is the width of the rug?

  1. 1

    Recall the area formula

    • Area = length x width
    • We know area = 24 m² and length = 6 m
  2. 2

    Use the inverse operation

    • To find width, divide area by length
    • Width = 24 ÷ 624 ÷ 6 = 4

The rug is 4 m wide.

The key insight: Division is the opposite of multiplication - use it to work backwards!

Common mix-up: 24 x 6 = 144 m. Multiplying makes the number bigger, but we need to find a smaller piece of the area.

Mistakes to watch for

These are the misconceptions we see most often in find missing dimensions, including the ones our practice questions are specifically designed to catch.

  • Using multiplication instead of division to find missing value
  • Confusing which formula to rearrange
  • For perimeter, forgetting to account for both pairs of sides

Build these skills first

Struggling with find missing dimensions? The real gap is often in one of these earlier topics.

Volume of CuboidsDivision Facts (Inverse of Times Tables)

More measurement practice

Know Metric Unit NamesUnderstand Metric PrefixesConvert Length UnitsConvert Mass UnitsConvert Capacity UnitsConvert Units with Decimals
26 questions on this topic alone

Master find missing dimensions and everything it unlocks

SEAGReady finds the exact step where your child gets stuck, teaches it with worked examples like the one above, and brings it back for review so it sticks.

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