Saving Money Rule of 72 vs Rule of 69.3 which is better to calculate saving?

[Yugocean]

The rules of 72 and 69.3 are mathematical ways to calculate the doubling time of your savings using the rate of interest.

Rule of 72
This rule is the simplest, in this the time is calculated by dividing 72 by the rate of interest. The formula is ( T = 72/r ) It is partially accurate but being simple it is most popular.

Rule of 69.3
This rule is based on the logarithmic function of 2 (0.69314), which translates to 69.3. In this, 1 has to be added and subtracted for every 3 digits of the interest rate. Apart from being complex, this rule has the limitation that it gives accurate information only up to 5% of the interest rate, for more than that the information is obtained from the E-M rule.

E-M Rule
Eckart–McHale second order is abbreviated as the E–M rule. This provides a multiplicative improvement of the rule of 69.3. In this, the result of Rule 69.3 is calculated from 200/(200−r). This can lead to predictions with accuracy at rates up to 20%.​

 

[saoussen5765]

I have bad memories with mathematiques so I hardly understand these rules because I have bad notes on maths. Best mark during full study career was 8. But I may choose rule of 69,3.

 

[Yugocean]

I have bad memories with mathematiques so I hardly understand these rules because I have bad notes on maths. Best mark during full study career was 8. But I may choose rule of 69,3.

Math may or may not be a favourite subject for people, but when it comes to numbers, everyone needs to use it. We calculate numbers in our daily lives, so why not calculate for savings and benefits? It will only help us avoid confusion.

If you have bad math skills, then the Rule of 69.3 is definitely not for you. The rule of 72 is easy to remember and will give a nearly accurate result if you use it properly.

With the knowledge of simple math, you will be able to determine the result using a piece of paper or calculator. It is so easy that after a while you will be able to calculate in your mind.

But the Rule of 69.3 is difficult; you first need to understand L ( n ), and it is easy only for those who understand, and they too will need to write down the formula order to use it.