Answer:
100 cm² , 1131 cm²
Explanation:
(a)
the surface area (SA) of a cuboid is calculated as
SA = 2(l × w) + 2(l × h) + 2(w × h)
where l is length, w is width and h is height
here l = 7 , w = 2 , h = 4 , then
SA = 2(7 × 2) + 2(7 × 4) + 2(2 × 4)
= 2(14) + 2(28) + 2(8)
= 28 + 56 + 16
= 100 cm²
(b)
the surface area (SA) of a cone is calculated as
SA = area of base + curved surface area
= πr² + πrs ( r is the radius of the base and s the slant height )
here r = 12 and s = 18 , then
SA = π × 12² + π × 12 × 18
= 144π + 216π
= 360π
≈ 1131 cm² ( to the nearest whole number )