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%.
