Ex 6.1

Chapter 6 Class 8 Cubes and Cube Roots
Serial order wise

### Transcript

Ex 6.1, 4 Parikshit makes a cuboid of plasticine of sides 5 cm, 2 cm, 5 cm. How many such cuboids will he need to form a cube? Here cuboids are joined to form a cube. So, Volume of cuboid × Number of cuboids = Volume of cube Volume of Cuboid Sides are 5, 2, 5 cm Length = 5 cm Breadth = 2 cm Height = 5 cm Volume = Length × Breadth × Height = 5 × 2 × 5 Volume of Cube Let side of cube = a Volume = Side3 = a3 Now, Volume of cuboid × Number of cuboids = Volume of cube 5 × 2 × 5 × Number of cuboids = a3 a3 = 5 × 2 × 5 × Number of cuboids Since on the left we have cube, we should have cube on the right as well To form cube on the right We multiply by 5 × 2 × 2 Thus, in a3 = 5 × 2 × 5 × Number of cuboids Putting Number of cuboids = 5 × 2 × 2 a3 = 5 × 2 × 5 × 5 × 2 × 2 a3 = 5 × 5 × 5 × 2 × 2 × 2 Therefore, Number of cuboids = 5 × 2 × 2 = 20

#### Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.