Ambillah enam benda-benda nyata yang ada di sekitar kalian, kemudian ukurlah dan perkirakan luas permukaan dan volumenya. Contoh: (lihat gambar di buku)
a. Toples
L = 2πr (r + t)
L = 2π7 (7 + 15)
L = 14π (22)
L = 308 cm²
V = πr²t
V = π x 7² x 15
V = π x 49 x 15
V = 735 cm³
b. Penghapus papan
L = 2 (pl + lt + pt)
L = 2 (8 x 4 + 4 x 4 + 8 x 4)
L = 2 (32 + 16 + 32)
L = 2 (80) = 160 cm²
V = plt = 8 x 4 x 4 = 128 cm³
c. Bola bekel
L = 4πr²
L = 4 x π x 2²
L = 4 x π x 4
L = 16π cm²
V = 4/3 πr³
V = 4/3 x π x 2³
V = 4/3 x π x 8
V = 32/3 π = 10,67π cm³
d. Pensil
L = πdt + πr² + πrs
L = π x 0,7 x 10 + π x 0,35² + π x 0,35 x 1,2
L = 7π + 0,1225π + 0,42π = 7,5425π cm²
T = √(s² – r²)
T = √(1,2² – 0,7²)
T = √(1,44 – 0,49)
T = √0,95 = 0,975 cm
V = V tabung + V kerucut
V = πr²t + ⅓ x πr² x T
V = π x 0,7² x 10 + ⅓ x π x 0,7² x 0,975
V = 4,9π + 0,16π = 5,06π cm³
e. Kotak tisu
L = 6 x s² = 6 x 9² = 6 x 81 = 486 cm²
V = s³ = 9³ = 729 cm³
f. Tempat sendok (tabung dan setengah bola)
L = πdt + πr² + ½ x 4πr²
L = π x 10 x 15 + π x 5² + ½ x 4 x π x 5²
L = 150π + 25π + 50π = 225π cm²
V = V tabung + V setengah bola
V = πr²t + 4/3 πr³
V = π x 5² x 15 + 4/3 x π x 5³
V = 375π + 166,67π = 541,67π cm³
