compound interest

Question

on the 1st of January carol invested some money into a bank

the account pays 2.5% compound interest per year

on 1st January 2015 carol withdrew 1000 pounds from the account

on 1st January 2016, she had 23517.6 in the account

 how much did carol originally invest in the account

 

Answer 1

2.5% compounding interest means

 100% + 2.5% = 102.5% = 1.025

 

(X - 1000)*1.025 = 23517.6

 

X - 1000 = 23517.6 / 1.025

 

X = 23517/6.1,025 + 1000

 

X = 23994