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I have two problems:

1.

How can i calculate compound interest when i want to reinvest a percentage of the sum of my principal and interest periodically?

To make it clearer,

Usually i use this formular for calculating compound interest: M = P( 1 + i )n.

This time i want to compound only a percentage of the sum of the principal and interest

2.

I want to compound the interest on the principal daily till the investment matures. ie. if am investing for one year, i want the daily interest to be compounded to the principal.

Thanks in advance

EDIT (to make question 1 clearer):

this is what am looking at:

i invest 1000 for a month, at the end of the month i get 1100 (principal plus interest), and i want to re-invest not the whole amount but 60% of the total amount for n periods. I hope its clearer. thanks

2 Answers 2