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The whole problem states, "In 383 days, Troy McLain earned $75 interest in an account paying 7.2% interest. Find (a) the principal at the beginning of the 383 days and (b) the amount in the account at the end of 383 days."tkhunny said:Interest compounding method?

Interest crediting method?

One must specify the whole problem.

Assuming you are dealing with compound interest:S. said:If a person earns $75 interest in an account paying 7.2% interest. Find the principal at the beginning of 383 days and the amount in the account at the end of 383 days. Actually, I know how to calculate the principal at the beginning of 383 days. Figuring out the problem at the end of the 383 days is what I need. Thanks

S = P(1 + i)^n

S = the total sum

P = the investing principal

i = the periodic interest in decimal form

n = the number of interest bearing periods

Compounded yearly, 1 + i = 1.072 and n = 383/365 = 1.04931

S - P = P(1 + 1.072^1.04931 - P = P[(1.072)^1.04931 - 1]

Therefore, P = 75/[(1.072)^1.04931 - 1] = $991.00

Compoundiong monthly, (1 + i = 1.006 and n = 12.6) the same process yields P = $958.00

Compounding dailly, (1 + i = 1.00019726 and n = 383) yields P = $955.78

The sums at the end of 383 days derive from the same formula.

Compounded monthly, for instance, S = 958(1.006^12.6 = $1033

The interest gained is $1033 - $958 = $75.00

I'll let you compute the other 2.

If you are dealing with simple interest, .072 per year, then your starting principal would be derived from S - P = 75 = .072(383/365)P making P = $992.71.

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This probably is not correct. There must be more information. One possible chunk of information not given in the problem statement is that you are working in a section entitled "Simple Interest". That would help clarify the problem.S. said:The whole problem states