Measurement · JHS2 Mathematics

Lesson notes

Learning Objectives

Indicator: B8.3.2.1.4 - Use the Pythagoras theorem to calculate the area of a triangle in real life problems.

By the end of the lesson, learners can:

Identify the base and perpendicular height of a triangle from a diagram or word problem, and state which side is the hypotenuse in a right-angled triangle.
Apply the Pythagoras theorem (a² + b² = c²) to find the missing height or base of a right-angled triangle, given the other two sides.
Calculate the area of a triangle using the formula Area = 1/2 × base × height after finding the required dimension using Pythagoras theorem.
Solve at least two real-life problems that require finding the area of a triangle using Pythagoras theorem, showing all working steps clearly.

Sign in with your phone number to read the full note and download the GES plan - free.

Sign in with phone number

Curriculum details

Strand: Geometry and Measurement (Strand 3)
Sub-strand: Measurement (3.2)
Content standard: B8.3.2.1 - Apply the Pythagoras theorem, the primary trigonometric ratios and the formulas for determining the area of a circle to solve real problems.
Indicator: B8.3.2.1.4 - Use the Pythagoras theorem to calculate the area of a triangle in real life problems.
Suggested placement: Term 3, Week 4 (Week 28 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: Mathematics, Common Core Programme (JHS1-JHS3), 2023, p. 145
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g.1 A boat travels 2m South and then 9m East. How far is the boat from its starting point?
E.g.2 Yeboah hangs a picture frame of width 15cm on the wall. The distance from the nail to the edge of the picture frame is 10cm.
(i) Find the length of the wire used to hang the picture frame.
(ii) Find the area of the triangle.
E.g.3 A ladder leans against a vertical wall of height 13m. If the foot of the ladder is 6m away from the wall, calculate the length of the ladder.
E.g.4 The length of a side of an equilateral triangle is 12cm. Find
i. the height of the triangle
ii. the area of the triangle
iii. the perimeter of the triangle