Answer: he open the account 9 years ago.
Step-by-step explanation:
The formula for determining simple interest is expressed as
I = PRT/100
Where
I represents interest paid on the amount deposited.
P represents the principal or amount deposited.
R represents interest rate
T represents the time for which the amount deposited was left in the account.
From the information given,
P = 400
R = 7.5%
I = 670 - 400 = $270
Therefore,
270 = (400 × 7.5 × T)/100 = 30T
T = 270/30
T = 9 years
