Joey opened a bank account 5 years ago with $100. today he has $1000 in the account. what is the percentage od increase?

To calculate the percentage increase:

First: Find out the difference (increase) between the two numbers you are comparing.
It is computed by: Increase = New Number - Original Number

Second: Divide the increase by the original number and multiply the answer by 100.
It is computed by: % increase = Increase ÷ Original Number × 100.

So in the problem:
First step:Increase = 1000 – 100
Increase = 900

Second:
% increase = 900 / 100 x 100%
increase = 900% increase