Mastering PSLE Semicircle Questions Made Simple

Understanding PSLE Semicircle Questions

Semicircle questions in PSLE Maths often challenge students by requiring a solid grasp of geometry concepts, formulas, and logical reasoning. These questions typically involve calculating areas, perimeters, or other dimensions based on semicircles and their related shapes.

In this guide, we’ll break down the topic with detailed explanations, examples, practical tips, and a practice section to ensure you're fully prepared for PSLE exams.

Key Concepts for Semicircles

What is a Semicircle?

A semicircle is half of a circle. It is formed by dividing a circle along its diameter. Key features include:

• Diameter: The longest straight line passing through the centre of the semicircle.
• Radius: Half the length of the diameter, extending from the centre to the edge.
• Arc: The curved boundary of the semicircle.

Important Formulas

Here are the critical formulas you need to memorise for semicircle calculations:

Measurement	Formula
Area of a Semicircle	(πr²) / 2
Perimeter of a Semicircle	πr + 2r
Circumference of the Full Circle	2πr

Use these formulas to tackle semicircle-related questions confidently.

Example: PSLE 2019 Semicircle Question

Let’s revisit a typical PSLE semicircle question:

The diameter of a semicircle is 14 cm. Calculate the perimeter of the semicircle.

Step-by-Step Solution

1. Find the radius by dividing the diameter by 2: 14 cm ÷ 2 = 7 cm.
2. Calculate the curved arc length using the formula πr: π × 7 = 22 cm (approximating π as 3.14).
3. Add the diameter to the arc length for the total perimeter: 22 cm + 14 cm = 36 cm.

Final Answer: The perimeter of the semicircle is 36 cm.

Practice Exercises

Test your understanding with these questions:

1. The radius of a semicircle is 8 cm. Calculate its area.
2. The diameter of a semicircle is 10 cm. Find its perimeter.
3. A semicircle has an arc length of 31.4 cm. What is its radius?

Answers are at the end of this blog post.

Exam Techniques

Tips for Tackling Semicircle Questions in PSLE

• Read the question carefully: Identify what is being asked—area, perimeter, or another measurement.
• Sketch the shape: A simple diagram can help you visualise the problem.
• Use correct formulas: Write down the applicable formula before solving.
• Double-check calculations: Accuracy is key in geometry questions.

Answers to Practice Exercises

1. Area = (πr²) / 2 = (3.14 × 8 × 8) / 2 = 100.48 cm².
2. Perimeter = πr + 2r = (3.14 × 5) + 10 = 25.7 cm.
3. Radius = Arc Length / π = 31.4 / 3.14 = 10 cm.

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