In how many years does a sum of money become three times of itself at the rate of $6\frac{1}{4}$ % simple interest per annum?

Let the principal be $P$.
If the sum becomes three times, then amount $A = 3P$.
So, simple interest:
$SI = A - P = 3P - P = 2P$

Using the formula:
$SI = \frac{P \times R \times T}{100}$

Given $R = 6\frac{1}{4} = 6.25%$,

$2P = \frac{P \times 6.25 \times T}{100}$

Cancel $P$:

$2 = \frac{6.25 \times T}{100}$

$T = \frac{2 \times 100}{6.25} = 32$

Answer: 32 years