In a bank, principal increases continuously at the rate of r% per year. Find the value of r if Rs 100 double itself in 10 years (loge2 = 0.6931).

let t be time

p be principal


r be rate of interest


according the information principal increases at the rate of r% per year.



Separating variables,



Integrating both sides,





Given that t = 0, p = 100.



Now, if t = 10, then p = 2×100 = 200


So,








So r is 6.93%.


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