Question

How many days will it take for a sum of $2000 to earn $40 interest if it is deposited in a bank paying simple interest at the rate of 3.6% per year?

What I did:
I=Prt

40=2000(3.6t)
40=7200t
40/7200=7200t/7200
t= .0055555556

Answer 1

In general, the formula I=Prt
has I in dollars
P in dollars
r : then annual interest year, expressed as a decimal
t: the time in years.

so:
40 = 2000(.036)t
t = 40/(2000(.036)) = .5555... or 5/9 years

to convert that to days, we have to multiply it by 365
so t = (5/9)(365) or 202.777. or appr 203 days

check:
P = 2000
r = .036
t = 203/365
I = 2000(.036)(203/365) = 40.04 , 4 cents off because we rounded to the nearest day

Answer 2

I = P*r*T.
40 = 2000*(0.036/365)*T.
40 = 0.1973T,
T = 203 Days.