Discussion of Question with ID = 020 under Simple-Interest

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The simple interest on a hypothetical investment is Rs. 5120. What is the principal amount if the rate per annum, time in years and the principal, all have the same numerical value?


Rs. 80.


Rs. 180.


Rs. 130.


Rs. 280.

Ans: a

If I is the interest, and principal is P, time is P, and rate is P, then, I = $(P × P × P)/100$. Which gives P = $√^3{100 × I}$, which is $√^3{100 × 5120}$, which is $√^3{1000 × 8 × 8 × 8}$ = Rs. 80.

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