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7 January, 10:58

108 identical books have a mass of 30 kg. Find

(i) the mass of 150 such books,

(ii) the number of such books that have a mass

of 20 kg.

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Answers (1)
  1. 7 January, 11:27
    0
    The mass of 150 books = 41.7kg

    The number of books that have mass 20kg = 72 books

    Step-by-step explanation:

    (I) Number of identical books = 108

    Mass of books = 30 kg

    Mass of 150 books = ?

    Let the mass of 150 books = x kg

    To find the mass of 150 books we will use ratio and proportion:

    108 books: 30kg = 150 books: x kg

    You can also write it like this because ratio can be written in division:

    108/30 = 150/x

    By cross multiplication:

    108x = 150*30

    108 x = 4500

    Divide both sides by 108

    108 x/108 = 4500/108

    x = 41.7

    Thus the mass of 150 books = 41.7kg

    (ii) The number of books that have a mass of 20 kg = ?

    Let assume that the number of books of mass 20 kg = y books

    We will again use ratio and proportion method.

    108 books: 30kg = y: 20kg

    We can write it as:

    108/30 = y/20

    By cross multiplication:

    108 * 20 = 30y

    2160 = 30y

    Divide both the terms by 30

    2160/30 = 30y/30

    72 = y

    Therefore the number of books that have mass 20kg = 72 books ...
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