Finding Rate when Principal and Time are given

We at ask-math believe that educational material should be free for everyone. Please use the content of this website for in-depth understanding of the concepts. Additionally, we have created and posted videos on our youtube.

We also offer One to One / Group Tutoring sessions / Homework help for Mathematics from Grade 4th to 12th for algebra, geometry, trigonometry, pre-calculus, and calculus for US, UK, Europe, South east Asia and UAE students.

Affiliations with Schools & Educational institutions are also welcome.

Please reach out to us on [email protected] / Whatsapp +919998367796 / Skype id: anitagovilkar.abhijit

We will be happy to post videos as per your requirements also. Do write to us.

In this section you will learn finding rate when principal and time are given in easy way.

The formula is given below :

                     S.I x 100
Rate % = R = -------------
                        P x T

Amount = A = P + S.I

Example :

1) P = $ 20,000 Amount = $ 21,800 and time T = 2 years. Find the rate.

Solution :
Amount = P + S.I

21,800 = 20,000 + S.I

S.I = 21,800 - 20,000

S.I = $ 1,800

                        S.I x 100
Rate % = R = -------------
                           P x T

                   1800 x 100
Rate % = R = -------------
                  20,000 x 2

                  180,000
Rate % = R = -------------
                    40,000

Rate = 4.5%

_______________________________________________________________
2) P = $ 625 Amount = $ 641.25 and time T = 146 days. Find the rate.

Solution :
Amount = P + S.I

641.25 = 625 + S.I

S.I =641.25 - 625

S.I = $ 16.25

                    S.I x 100
Rate % = R = -------------
                       P x T

As the rate is given in days so T = 146 days = 146/365 =0.4 years

                   16.25 x 100
Rate % = R = -------------
                   625 x 0.4

                      1625
Rate % = R = -------------
                        250

Rate = 6.5%
______________________________________________________________
3) At what rate percent will a sum of money treble itself in 12 years?

Solution :
A = 3P
t = 12 years
A = P + I
But I = PRT/100
∴ A = P - (PRT/100)
3P = P - (PRx12/100)
3P- P = 12PRT/100
2P = (12 x P x R)/100
cross multiply
2P x 100 = 12 PR
200P = 12 PR
R = 200P/12P
∴ R = 200/12
∴ R = 50/3 % = 16.66%
Simple Interest (S.I)

Finding rate when Principal and time are given
Finding time when Principal and rate are given
Solved examples on Simple Interest

Home Page

Russia-Ukraine crisis update - 3rd Mar 2022

The UN General assembly voted at an emergency session to demand an immediate halt to Moscow's attack on Ukraine and withdrawal of Russian troops.