1 / 13

Cubes & cuboids

Cubes & cuboids. h. l. b. Exercise1:. Cuboids. 5. 9. 6. For this cuboid, calculate, in cm’s:. (i) The volume. (i) The surface area. Solution:. Volume:. 5. Cuboids. V = lbh. => V = (9)(6)(5). 9. 6. => V = 270cm ³. Surface area:. SA = 2lb + 2lh + 2bh.

derry
Download Presentation

Cubes & cuboids

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cubes & cuboids h l b

  2. Exercise1: Cuboids 5 9 6 For this cuboid, calculate, in cm’s: (i) The volume. (i) The surface area.

  3. Solution: Volume: 5 Cuboids V = lbh => V = (9)(6)(5) 9 6 => V = 270cm³ Surface area: SA = 2lb + 2lh + 2bh => SA = 2(9x6) + 2(9x5) + 2(6x5) => SA = 2(54) + 2(45) + 2(30) => SA = 108 + 90 + 60 => SA = 258cm²

  4. Exercise2: Cubes 7 7 7 For this cube, calculate, in cm’s: (i) The volume. (i) The surface area.

  5. Solution: Volume: 7 Cubes V = l³ 7 7 => V = (7)(7)(7) => V = 343cm³ Surface area: SA = 6l² => SA = 6(7²) => SA = 6(49) => SA = 294cm²

  6. Exercise3: Find the missing dimension h 8 14 The volume of this rectangular block is 560cm³. Given a length of 14cm and a breadth of 8cm, calculate its: (i) Height. (i) Surface area.

  7. Solution: Height: h V = lbh = 560cm³ Find the missing dimension 8 => (14)(8)h = 560 14 => 112h = 560 => h = 560 / 112 => h = 5cm Surface area: SA = 2lb + 2lh + 2bh => SA = 2(14)(8) + 2(14)(5) + 2(8)(5) => SA = 2lb + 2lh + 2bh => SA = 224 + 140 + 80 => SA = 444cm²

  8. Exercise4: Find the volume The surface area of this cube is 54cm² Calculate its volume

  9. Solution: Surface area = 54cm² Find the volume => 6l² = 54 => l² = 9 => l = 3cm Volume = l³ => V = 3³ => V = 27cm³

  10. Exercise5: A rectangular glass tank has internal dimensions of length 1.2m, breadth 80cm, and height 60cm. Practical problem (i) How many litres of water can it contain? (ii) If water is poured into the tank at the rate of 8 litres per minute, how long does it take to fill the tank?

  11. Solution: Step1: Visualize the problem. Step2: As 1litre = 1000cm³, change all dimensions to centimetres. Practical problem Step3: Find the volume of the tank. V = lbh = (120)(80)(60). => V = 576000cm³. (i) No. of litres = (Volume of tank in cm³) / (1000cm³) => Number of litres = 576000/1000 => 576litres of water can be contained in this tank. (ii) Time taken to fill the tank = (volume of tank in litres) / (number of litres poured per minute). => Time taken to fill the tank = 576 / 8 => Time taken to fill the tank = 72minutes

  12. Exercise6: A rectangular block of metal has dimensions 48cm by 24cm by 16cm. It is melted down and recast into cubes of length 8cm, without loss of volume. Practical problem How many cubes will it cast?

  13. Solution: Step1: Visualize the problem. Step2: Find the volume of the block. Practical problem Volume = lbh => V = (48)(16)(24) => V = 18432cm³ Step3: Find the volume of one of the melted down cubes. Volume = l³ => V = 8³ => V = 512cm² Step4: Find how many of these cubes will fit into the block. No. of recast cubes = Volume of block / Volume of cube. => No. of recast cubes = 18432 / 512 => 36 cubes will be cast from this metal block.

More Related