New
New
Year 5

# Calculate missing dimensions in rectangles and compound rectilinear shapes

I can calculate missing dimensions in rectangles and compound rectilinear shapes.

New
New
Year 5

# Calculate missing dimensions in rectangles and compound rectilinear shapes

I can calculate missing dimensions in rectangles and compound rectilinear shapes.

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## Lesson details

### Key learning points

1. Division is used to calculate a missing dimension when the area and the other dimension are known.
2. Inverse operations are used to calculate missing dimensions when areas are known.
3. Compare different methods to decompose shapes and decide which is the most efficient.

### Common misconception

Applying known facts and strategies to solve problems involving division. Being able to break down a problem into steps when it comes to compound shapes.

Provide opportunities to discuss approaches and highlight the efficient strategies and approaches. Acknowledge that there is more than one way to solve a problem whilst focusing on efficient and effective strategies.

### Keywords

• Compound - A compound shape is made up of two or more shapes.

• Dimension - A dimension is a measurement of length in one direction. Width and height are examples of the dimensions of 2D shapes.

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
x 7 = 56
Q2.
96 = x 8
Q3.
Which of these compound rectilinear shapes have a total area of 60 m²?
a
Q4.
Which calculation would you use to calculate the area with the information you have been given?
72 cm² − 10 cm² = 62 cm²
Correct answer: 42 cm² + 20 cm² = 62cm²
48 cm² + 14 cm² = 62 cm²
Q5.
Jun worked out the area of a compound shape. Which of these shapes was he calculating the area of?
Correct Answer: An image in a quiz
Q6.
What is the area of the grey path around the pond?
Correct Answer: 46m², 46 m², 46m2, 46 m2

## Exit quiz

### 6 Questions

Q1.
What is the missing dimension
Correct Answer: 4 cm, 4cm, 4, 4CM, 4 CM
Q2.
What is the missing dimension?
Correct Answer: 7 cm, 7cm, 7, 7 CM, 7CM
Q3.
What is the missing dimension?
Correct Answer: 23 cm, 23cm, 23, 23 CM, 23CM
Q4.
The area of this compound shape is 116 cm². What is the missing dimension?
6 cm