B PLUSTOPPER

  Surface Area, Volume and Capacity Exercise 21A – Selina Concise Mathematics Class 8 ICSE Solutions Question 1. Find the volume and the total surface area of a cuboid, whose : (i) length = 15 cm, breadth = 10 cm and height = 8 cm. (ii) l = 3.5 m, b = 2.6 m and h = 90 cm, Solution: (i) Length =15 cm, Breadth = 10 cm, Height = 8 cm. Volume of a cuboid = Length x Breadth x Height = 15 x 10 x 8 =1200 cm 3 . Total surface area of a cuboid 2 (l x b + b x h + h x l) = 2 (15 x 10 + 10 x 8 + 8 x 15) = 2(150 + 80 +120) = 2 x 350 = 700 cm 2 (ii) Length = 3.5 m Breadth = 2.6 m, Height = 90 cm =  90 100  m = 0.9 m. Volume of a cuboid = l x b x h = 3.5 x 2.6 x 0.9 = 8.19 m 3 Total surface area of a cuboid = 2(l x b + b x h + h x l) = 2 (3.5 x 2.6 + 2.6 x 0.9 + 0.9 x 3.5) = 2 (910 + 2.34 + 3.15) = 2(14.59)= 29.18 m 2 Question 2. (i) The volume of a cuboid is 3456 cm 3 . If its length = 24 cm and breadth = 18 cm ; find its height. (ii) The volume of a cuboid is 7.68 m 3 . If its length = 3.2 m and he