The barrel of a fountain pen, cylindrical in shape, is 7 cm long and 5 mm in diameter. A full barrel of ink in the pin is used up on writing 3300 words on an average. How many words can be written in a bottle of ink containing one-fifth of a Litre?


Let us first calculate the volume of barrel of pen that is of cylindrical shape


For barrel,


Base diameter = 5 mm = 0.5 cm [As 1 cm = 10 mm]


Base radius, r = 0.25 cm


[as radius = diameter/2]


Height, h = 7 cm


As we know,


Volume of a cylinder = πr2h


Where r is base radius and h is the height of cylinder


volume of barrel


Volume of barrel


So,


1.375 cm3 of ink can write 3300 words


No of words that can be written by 1 cm^3


[ Also of a liter i.e. 0.2 L and we know


1 L = 1000 cm3


0.2 L = 200 cm3 ]


No of words that can be written by 200 cm3 = 2400(200) = 480000 words


So,


One-fifth of a liter ink can write 480000 words on an average.


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