The angle and radius of a sector

A FULL LESSON on calculating the angle and radius of a sector, given its area or arc length.

Assumed prior knowledge:

• Rounding with significant figures and decimals.
• Simplifying expressions.
• Fractions of amounts.
• Solving equations using the balancing method.

We are learning about: The angle and radius of a sector.
We are learning to: Calculate the angle and radius of a sector, given its area, arc length or perimeter.

Differentiated objectives:

• Developing learners will be able to calculate the angle of a sector, given its area, arc length or perimeter.
• Secure learners will be able to calculate the radius of a sector, given its area, arc length or perimeter.
• Excelling learners will be able to solve unfamiliar problems using their knowledge calculating the angle and radius of a sector.

Starter: Spot the mistake activity: calculating the area of a sector.
Main:

• Examples to find the angle of a sector given its area or arc length.
• Standard questions with diagrams progressing to worded questions.
• Two further examples to find the radius of a sector given its area or arc length.
• Standard questions with diagrams, following on to two problem solving questions.
  Plenary: Find two pairs of integer values for the radius and an acute angle which give an arc length of 2π?

Extra:

• Examples provided on printable worksheet. Similar to a bookmark shape, the students find it easy to stick this in on the (I use) left side of the page in their books. It saves time from writing down large amounts of text and drawing diagrams. More time to focus on learning!!
• Booklet with all questions provided as worksheet to stick in books.

Any feedback is appreciated!