6.4.2 Surface Area of Three Dimensional Shapes, PT3 Focus Practice
Question 4:
Sphere below has a surface area of 221.76 cm2.
![](http://pt3mathematics.blog.onlinetuition.com.my/wp-content/uploads/sites/6/2017/06/Picture89-1.png)
Calculate its radius.
Solution:
Surface area of sphere = 4πr2
Question 4:
Sphere below has a surface area of 221.76 cm2.
![](http://pt3mathematics.blog.onlinetuition.com.my/wp-content/uploads/sites/6/2017/06/Picture89-1.png)
Calculate its radius.
Solution:
Surface area of sphere = 4πr2
Question 5:
Diagram below shows a right pyramid with a square base.
![](http://pt3mathematics.blog.onlinetuition.com.my/wp-content/uploads/sites/6/2017/06/Picture90.png)
Given the height of the pyramid is 4 cm.
Calculate the total surface area, in cm2, of the right pyramid.
Solution:
h2 = 32 + 42
= 9 + 16
= 25
h = √25 = 5 cm2
Total surface area of the right pyramid
= Base area + 4 (Area of triangle)
= (6 × 6) + 4 × 4 (½ × 6 × 5)
= 36 + 60
= 96 cm2
Diagram below shows a right pyramid with a square base.
![](http://pt3mathematics.blog.onlinetuition.com.my/wp-content/uploads/sites/6/2017/06/Picture90.png)
Given the height of the pyramid is 4 cm.
Calculate the total surface area, in cm2, of the right pyramid.
Solution:
![](http://pt3mathematics.blog.onlinetuition.com.my/wp-content/uploads/sites/6/2017/06/Picture91.png)
= 9 + 16
= 25
h = √25 = 5 cm2
Total surface area of the right pyramid
= Base area + 4 (Area of triangle)
= (6 × 6) + 4 × 4 (½ × 6 × 5)
= 36 + 60
= 96 cm2