area and volume (f3)

Question 11

Curved surface area of cone formula = πrL
where:
π= Pi
r= radius
L= slant height

84π=πrL
84π=πr (12)
84/12=r
r=7cm

Question 12

Curved surface area of cone formula = πrL
176π=πrL
176π=π(8)L
176/8=L
L = 22cm

Question 13

Part A: Pythagoras' Theorem = a^2 + b^2 = c^2
a= radius (which is 30/2 = 15cm)
b=height (which is 20cm
c= slant height
15^2 + 20^2 = c^2
625 = c^2
c= 25cm

Part B: Total surface area = area of circle + area of curved surface area
=(π*r^2) + (πrL)
=(π*15^2) + (π(15)(25))
=1884.955592cm^2
=1884.96cm^2 (to 2 dp)