## Calculating concern : Principal, Rate, and Time Are Known

When you know the chief measure, the rate, and the prison term, the amount of matter to can be calculated by using the formula :

I = Prt

For the above calculation, you have $ 4,500.00 to invest ( or borrow ) with a rate of 9.5 percentage for a six-year menstruation of time .

## Calculating Interest Earned When Principal, Rate, and Time Are Known

Calculate the amount of sake on $ 8,700.00 when earning 3.25 percentage per annum for three years. once again, you can use the I = Prt formula to determine the full measure of concern earned. Check with your calculator .

## Calculating Interest When the Time Is Given in Days

Suppose you want to borrow $ 6,300 from March 15, 2004, until January 20, 2005, at a rate of 8 percentage. The formula will still be I = Prt ; however, you need to calculate the days .

To do indeed, do not count the sidereal day the money is borrowed or the day the money is returned. To determine the days : March = 16, April = 30, May = 31, June = 30, July = 31, August = 31, September = 30, October = 31, November = 30, December = 31, January = 19. consequently, the meter is 310/365. A sum of 310 days out of 365. This is entered into the metric ton for the formula .

## What Is the Interest on $ 890 at 12.5 percentage for 261 Days ?

once again, apply the formula :

I = Prt

You have all the information you need to determine the interest in this question. Remember, 261/365 days is the calculation for deoxythymidine monophosphate = time .

## Find the Principal When You Know the Interest, Rate, and Time

What amount of principal will earn matter to of $ 175.50 at 6.5 percentage in eight months ? once again, use the derive formula of :

Read more: How to Calculate Student Loan Interest

I = Prt

which becomes :

P = I/rt

Use the exercise above to help you. Remember, eight months can be converted to days or you can use 8/12 and move the 12 into the numerator in the rule .

## What Sum of Money Can You Invest for 300 Days at 5.5 percentage to Earn $ 93.80 ?

As above, use the derive rule of :

I = Prt

which will be :

P = I/rt

In this event, you have 300 days, which will look like 300/365 in the formula. Remember to move the 365 into the numerator to enable the formula to work. Get out your calculator and check your answer with the solution above .

## What annual pastime Rate Is Needed for $ 2,100 to Earn $ 122.50 in 14 Months ?

When the total of interest, the principal, and the time menstruation are known, you can use the derive formula from the dim-witted interest formula to determine the rate, as follows :

I = Prt

becomes

r = I/Pt

Remember to use 14/12 for time and move the 12 to the numerator in the formula above. Get your calculator and check to see if you ‘re correct .

Edited by Anne Marie Helmenstine, Ph.D .

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