Measurement of Area and Volume 



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20. The volume of a rectangular slab may be 

 found by performing 



EXPERIMENT 10. From a bar of soap or a lump of 

 plasticine cut out carefully a brick-shaped slab 6 cm. 

 long, 4 cm. wide and 3 cm. deep. (Or procure a small 

 cardboard box of these or similar internal dimensions, 

 pack it tightly with plasticine and then carefully remove 

 the cardboard faces.) Mark off the consecutive centi- 

 metres along the four long edges of the slab and join 

 the marks by parallel lines. (See Fig. 12.) Carefully 



Fig. 12. 



cut the slab along these lines. This is most readily 

 done with a length of fine wire after the fashion of a 

 grocer cutting cheese. The six smaller slabs thus 

 formed have evidently the same total volume as that 

 of the original slab. Mark out one face of one of the 

 smaller slabs in square centimetres as shown in Fig. 13. 

 Cut the slab along the lines thus obtained. It will be 

 noted that each of the portions thus formed is a cube 

 and that its edge is 1 cm. long, i.e. it has a volume of 



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