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Rajan@2021
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A child puts one five rupee coin her saving in the piggy bank on the first day. She increases her saving by one five rupee-coin daily. If the piggy bank can hold 190 coins of five rupees in all, find the number of days she continue to put the five rupee coins into it and find the total money she saved.

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Sir please give me a detailed solution of this question from arithmetic progression chapter in which we have been asked to find the number of days a child can contribute to put the five-rupee coins into piggy bank and also we are asked to find the total money she saved if she puts one five rupee coin her saving in the piggy bank on the first day. She increases her saving by one five rupee-coin daily. If the piggy bank can hold 190 coins of five rupees in all.

Book RS Aggarwal, Class 10, chapter 5C, question no 49

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1 Answer

  1.  Child’s daily input is 5, 10, 15, —
    & the number of coins on each days are
    1, 2, 3, _ _ _  A.P with a = 1, d = 1 where Sn190
    2n(2+(n1)1)190
    n+2n^22n190
    n^2+n380
    n^2+n3800
    n^2+20n19n3800
    n(n+20)19(n+20)0
    (n19)(n+20)0
    nϵ[20,19]
     she can
    put coins for 19 days
    For amount, 5,10,15,...AP=5 (1, 2, 3,_ _ _ )
    Sum of 19 terms =[5×19(20)]/2​                                          =Rs.950

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