Bank Doubling the Amount Brain Teaser

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You went to a bank near your newly possessed home. The bank’s policies are weird, but you decided to open the account anyhow with a certain amount. The policy is that at the end of each year, the total amount gets doubled and $65 is deducted from that amount. After 6 years, when the you checks your account balance, the total amount was $0.

Can you find out what was the original amount that you had deposited in the bank?

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  • 2 Answer(s)

    Answer- $63.984375

    Explanation:
    Suppose that transaction are digital and hence we can transact in fractions in bank account. The following is the solution:

    Year Amount Interest and Deduction
    Start $63.984375
    Y1 End $62.968750 $63.984375 * 2 – $65
    Y2 End $60.937500 $62.96875* 2 – $65
    Y3 End $56.875000 $60.9375 * 2 – $65
    Y4 End $48.750000 $56.875 * 2 – $65
    Y5 End $32.500000 $48.75 * 2 – $65
    Y6 End $0.000000 $32.5 * 2 – $65 = 0

    Detective Expert Answered on 12th May 2017.
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    12.03125
    2(2(2(2(2p-65$)-65$)-65$)-65$)-65$=0
    p=12.03125

    sachin Starter Answered on 11th May 2017.
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