1. Area Revision Lesson Area of a parallelogram area of a triangle
re-arranging formulae to find missing lengths
area of compound shapes
square numbers and square roots

2. Re-arranging Formulae to Find Missing Lengths
𝑨𝒓𝒆𝒂 𝒐𝒇 𝒂 𝑹𝒆𝒄𝒕𝒂𝒏𝒈𝒍𝒆 = 𝑳𝒆𝒏𝒈𝒕𝒉 × 𝑩𝒓𝒆𝒂𝒅𝒕𝒉
𝑨 = 𝑳 × 𝑩
Given A and need to find L?
𝑨 = 𝑳 × 𝑩
𝑨÷𝑩 = 𝑳
𝑳=𝑨÷𝑩
Given A and need to find B?
𝑨 = 𝑳 × 𝑩
𝑨÷𝑳 =𝑩
𝑩=𝑨÷𝑳
A = 30 and B = 3 Find L A = 45 and L = 9 Find B

3. Re-arranging Formulae to Find Missing Lengths
𝑨𝒓𝒆𝒂 𝒐𝒇 𝒂 𝑷𝒂𝒓𝒂𝒍𝒍𝒆𝒍𝒐𝒈𝒓𝒂𝒎 =𝑩𝒂𝒔𝒆 ×𝑯𝒆𝒊𝒈𝒉𝒕
𝑨 =𝑩 ×𝑯
Given A and need to find H?
𝑨 =𝑩 ×𝑯
𝑨÷𝑩 =𝑯
𝑯=𝑨÷𝑩
Given A and need to find B?
𝑨 =𝑩 ×𝑯
𝑨÷𝑯 =𝑩
𝑩=𝑨÷𝑯
A = 42 B = 7 Find H A = H = 5 Find B

4. Re-arranging Formulae to Find Missing Lengths
Given A and need to find H?
𝑨= 𝑩 × 𝑯 𝟐
𝑨×𝟐 =𝑩×𝑯
𝟐𝑨 = 𝑩 × 𝑯
𝟐𝑨 𝑩 = 𝑯
Given A and need to find B?
𝑨= 𝑩 × 𝑯 𝟐
𝑨×𝟐 =𝑩×𝑯
𝟐𝑨 = 𝑩 × 𝑯
𝟐𝑨 𝑯 =𝑩
𝑨𝒓𝒆𝒂 𝒐𝒇 𝒂 𝑻𝒓𝒊𝒂𝒏𝒈𝒍𝒆 = 𝑩𝒂𝒔𝒆 × 𝑯𝒆𝒊𝒈𝒉𝒕 𝟐
𝑨= 𝑩 × 𝑯 𝟐
A = B = 4 Find H A = H = 6 Find B

5. ALWAYS IGNORE THE SLANTING LENGTHS!
Height
Triangle
Base
EXAMPLES 1) 2) 5m 4m
7cm
5cm 3m
11cm
12m
Work out the area of the parallelogram
Work out the area of the triangle
AREA OF PARALLELOGRAM = 11 x 5
𝟏𝟐×𝟑 𝟐
AREA OF TRIANGLE =
AREA OF PARALLELOGRAM =
55cm 2
AREA OF TRIANGLE =
18cm 2 5

6. THE SHAPE SPLITS INTO A PARALLELOGRAM AND TRIANGLE
Find the area of the shape
THE SHAPE SPLITS INTO A PARALLELOGRAM AND TRIANGLE
AREA OF PARALLELOGRAM = 9 x 5
AREA OF PARALLELOGRAM =
45cm 2
12cm 9 x 7 2
31.5cm 2
5cm
AREA OF SHAPE =
AREA OF SHAPE = 76.5cm 2
9cm 6

7. Pg 149-150 Ex 7c 7, 8, 16, 20, 33, 35, 44, 47 ANSWERS TO 3 SIGNIFICANT FIGURES
𝟔𝟓𝟎
=𝟐𝟓.𝟓 𝟔𝟒 =𝟖
𝟏𝟒𝟒
=𝟏𝟐
𝟒𝟎𝟏𝟐𝟎𝟎𝟎
=𝟐𝟎𝟎𝟎
𝟏.𝟏 𝟐
=𝟏.𝟐𝟏 𝟖𝟓
=𝟗.𝟐𝟐𝒄𝒎
𝟒𝟎 𝟐
=𝟏𝟔𝟎𝟎 𝟑𝟐
=𝟓.𝟔𝟔𝒎

8. Area Revision Sheet
For Thursday 30th March