Question

Sebuah kerucut volumenya 37,68 cm³, tingginya 4 cm. Luas seluruh sisi kerucut adalah.. (phi = 3,14)

Answer 1

V=1/3 phi r^2 t
37,68 = 1/3 * 3,14 * r^2 * 4
37,68 * 3= 12,56*r^2
113,04=12,56 r^2
r^3 = 113,04/ 12,56
r= akar 9
r=3

s= akr t^2 +r^2
= akr 4^2 + 3^2
= akr 16 + 9
= akr 25 = 5

jdi luas = phi rs+phi r^2
= 3,14 (3)(5) + 3,14 (3)^2
=47,1 + 28,26 = 75,36 cm^2

Answer 2

Dik : v = 37.68 cm3
t = 4 cm
dit :Lp =....?
jwb : v = 1/3 πr2t
37.68 = 1/3 x 3.14 x r2 x
37.68 x 3 = 3.14 x r2 x 4
113.04 = 12.56 r2
r2 = 9
r. = √9 = 3 cm

~ s = √r2 + t2
= √3^ + 4^
= √9 + 16
= √25 cm
= 5 cm

Luas Permukaan = πr(r+s)
= 3.14 x 3 (3+5)
= 9.42 × 8
= 75.36 cm2