সঠিক উত্তর হচ্ছে: ১০.০০ টাকা
ব্যাখ্যা: Let the principal be x
\nTime = 10 years
\nAmount after 10 years gets doubled
\nSo amount = 2x
\nsimple interest = amount - principal
\nsimple interest = 2x - x = x
\nRate per annum = SI × 100 / P × T
\n= x × 100 / x × 10
\n100x/ 10x = 10
\nSo rate per annum = 10%.
