Everything Maths Grade 10

Step 3: Find the sum of the areas

9

p

3 + 90 =105,6 cm^2

Step 4: Write the final answer

The surface area of the triangular pyramid is 105,6 cm^2.

Worked example 9: Finding the surface area of a cone

QUESTION

Find the surface area of the following cone (correct to 1 decimal place):

4 cm

14 cm

h

SOLUTION

Step 1: Find the area of the base

area of base circle=r^2

= 42

= 16

Step 2: Find the area of the walls

area of sides=rh

To find the slant height,h, we use the theorem of Pythagoras:

Chapter 13. Measurements 435