In a particular time, a sum becomes 6 times of itself on simple interest at the rate of 10% per annum. What is the rate of interest if the same sum becomes 16 times of itself in the same duration?

30%

                Principal   :  Amount   :    S.I.   ⇒     Rate

6 times ⇒        1       :        6       :     5     ⇒      10%

                                                         ⇓ ×3          ⇓ ×3

16 times ⇒        1       :        16      :     15     ⇒      30%