Use the area of a triangle  to calculate unknown measurements

Maths

In this unit pupils will explain how to calculate the area of a parallelogram and a triangle describing the relationship between scale factors and side lengths. They will describe positions in all four quadrants drawing and translating simple shapes and reflecting them in the axes In the future unit pupils extend their knowledge of plotting coordinates by now plotting non-integer values.

In the prior unit pupils used knowledge of shape properties to draw, sketch and identify shapes. In this unit pupils will explain how to calculate the area of a parallelogram and a triangle. They will describe the relationship between scale factors and side lengths of two shapes. They will describe positions in all 4 quadrants drawing and translating simple shapes and reflecting them in the axes.

Area, perimeter, position and direction

Complete the formula you could use if the area and perpendicular height of a triangle are known but the base is not: base = area × {{  }} ÷ perpendicular height.

Complete the formula you could use if the area and base of a triangle are known but the perpendicular height is not: perpendicular height = area × 2 ÷ {{  }}

Look at the triangle. The missing perpendicular height is {{  }} cm

Look at the triangle. The missing perpendicular height is {{  }} cm.

Look at the triangle. The missing base length is {{  }} cm.

Base = 3 cm, Perpendicular height = 7 cm 

Base = 12 cm, Perpendicular height = 7 cm 

Base = 4 cm, Perpendicular height = 21 cm

A triangle has an area of 42 cm². Which of these could be its base and perpendicular height?

Which of the dotted lines shows the perpendicular height of the triangle from the labelled base?

Complete the formula for the area of a triangle. Area = base × perpendicular height ÷ {{ }} 

Calculate the area of the triangle. {{  }} cm².

Calculate the area of a triangle with a base of 15 cm and a perpendicular height of 8 cm. {{  }} cm².

If a parallelogram has an area of 56 cm² and a base of 8 cm, what is the missing perpendicular height? {{  }} cm.

This lesson will soon be taken down.

Use the area of a triangle to calculate unknown measurements

Lesson outcome