Question

Tolong dibantu no 78 dan 79 dengan cara dan jawaban yang tepat jangan asal!!!!

Answer 1

78. Luas selimut tabung = 2πr . t
1.256 = 2 . 3,14 . r . 20
1.256 = 125,6r
r = 10 cm

Luas tabung tanpa tutup
= Luas alas + Luas selimut
= πr² + 1256
= 3,14 . 10² + 1256
= 314 + 1256
= 1.570 cm² (D)

79.Vtabung = L alas . tinggi
2.310.000 = πr² . t
2.310.000 = 22/7 . 70 . 70 . t
2.310.000 = 22 . 10. 70 . t
2.310.000 = 15400t
t = 150 cm

L selimut tabung = 2πr . t
= 2 . 22/7 . 70 . 150
= 2 . 22 . 10 . 15
= 66.000 cm²
= 660 dm³ (D)

Answer 2

No  78) 
luas selimut kerucut = 2 x phi x r x t
1256 = 2 x 3,14 x r x 20
r = 1256 / 125,6
r = 10

luas tabung tanpa tutup = phi x r x (r + 2t)
= 3,14 x 10 x (10+40)
= 3,14 x 10 x 50
= 1570

jawaban D

no 79)

volum = phi x r^2 x t
2310.000 = 22/7 x 70 x 70 x t
t = 2310.000 / 15400
t = 150 cm

luas selimut = 2 x phi x r x t
= 2 x 22/7 x 70 x 150
= 66.000 cm^2
= 660 dm^2
jawaban  D