4.6 Find The Principal, Rate, and Time of ...

This section explains the use of I = PRT in different forms. It is used to calculate principal, rate or time, given either interest or any of the other two values is known.

1.	Finding the principal. When interest, rate, and time are known, the principal can be computed using the following formula:

4.6 Find The Principal, Rate, and Time of ...

Example 23
Calculate the principal of a 6% note that earned RM 160 in 60 days.

Solution:


The principal is RM 16,000.

4.6 Find The Principal, Rate, and Time of ...

2.	Finding the rate. To determine the rate of interest, the following formula is used:

Example 24
Calculate the rate of interest for a RM 16,000 note that earned RM 250 in 60 days.

Solution:

The rate is 9%.

4.6 Find The Principal, Rate, and Time of ...

3.	Finding the time Time should be stated in years or a fraction of a year. The formula to find time:

Example 25
Find the time, stated in years; it will take a RM 6,000 loan to earn RM 400 interest at a 5% rate.

Solution:

4.6 Find The Principal, Rate, and Time of ...

Example 26
Find the time, stated in months; it will take RM 6,000 to earn RM400 interest at a 5% rate.

Solution:


Example 27
Find the number of days, using the ordinary interest method; it will take a loan of RM 6,000 to earn interest of RM 480 at a 5% rate.

Solution: