It’s the ‘Rule of 72’
Gives the compound annual rate
At which a rupee grows to two
Just divide 72
With the number of years
Here, 72/10 is the answer
if your rupee in 10 years
Grows from one to three
That’s 11.4% a year
‘Rule of 114’, you’ll see
Just divide 114
By the number of years
Here, 114/10 does the trick
We don’t need any seers
if your rupee in 10 years
Grows from one to four
That’s a cool 14.4% p.a.
By the ‘Rule of 144’
Simply divide 144
By the number of years
Here, 144/10 works like magic
They also work in reverse
The Rules of 144, 114, and 72
So, if you know the rate
In a jiffy, you’ll find the period too
So, if at 8% per annum
Your money grows and doubles
It would take 9 years