b) Luas = 2 x π x 12 x (12 + 40)
= 1.248π dm2
c) Luas = 2 x π x 1 x (1 + 2)
= 6π m2
d) Luas = π x 9 x (9 + 15)
= 216π cm2
e) Luas = π x 8 x (8 + 17)
= 200π dm2
f) Luas = π x 1 x (1 + 2)
= 3π m2
g) Luas = 4 x π x 12 x 12
= 576π cm2
h) Luas = 4 x π x 5 x 5
= 100π m2
i) Luas = 4 x π x 8 x 8
= 256π dm2
j) Luas = 2 x π x 6 x (6 + 9)
= 180π m2
k) Luas = π x 6 x (6 + 3√13)
= (36 + 18√13)π dm2