Smile 發問於 科學及數學數學 · 11 月前

Maths problem: how to do (c) and (d), thanks?

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  • SC147
    Lv 6
    11 月前
    最愛解答

    (c) Methods of buying 2 books using ≦ $50 are:

    {16+16,16+20,16+28,16+34, 20+20, 20+28}

    ∴ no. of ways buying 2 books using ≦ $50

    = C(6,2)+6*8+6*4+6*6+C(8,2)+8*4

    = 15+48+24+36+28+32

    = 183

    (d) Methods of buying 1 book using ≦ $50 are:

    {16, 20, 28, 34}

    ∴ no. of ways buying 1 book using ≦ $5

    = 6*8*4*6

    = 1,152‬

    Method of buying 3 books using ≦ $50 is:

    {16+16+16}

    ∴ no. of ways buying 1 book using ≦ $5

    = C(6,3)

    = 20

    ∴ no. of ways of buying any no. of books using ≦ $50

    = 183+1152+20

    = 1,355

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