Where, A = amount

P = Principal

r = rate in percent

n = time in years.

1) At what rate percent P.a , compound interest will $ 10,000 amount to $ 13,310 in three years?

Here, P = $ 10,000 ; A = $ 13,310 ; n = 3 years

A = P ( 1 + r)

13,310 = 10,000( 1 + r )

13,310/10,000 = ( 1 + r )

1331/1000 = ( 1 + r)

( 11/10)

11/10 = 1 + r

11/10 – 1 = r

( 11 – 10)/10 = r

1/10 = r

As rate is in percent so, r = (1/10) x 100

Rate = 10 % P.a.

2) At what rate percent compound interest P.a. will $640 amount to $ 774.40 in 2 years ?

Here, P = $ 640 ; A = $ 774.40 ; n = 2 years

A = P ( 1 + r)

774.40 = 640 ( 1 + r )

774.40 /640 = ( 1 + r )

77440 /64000 = ( 1 + r)

( 88/80)

(11/10)

11/10 = 1 + r

11/10 – 1 = r

( 11 – 10)/10 = r

1/10 = r

As rate is in percent so, r = (1/10) x 100

Rate = 10 % P.a.

• Find Compound Interest when interest is compounded Half yearly

• Find Compound Interest when interest is compounded Quarterly

• Find CI when interest is compounded annually but Rates are different

• Finding Principal

• Finding Time Period of Investment

• Finding Rate of Interest

BYJU'S

GMAT

GRE

1st Grade

2nd Grade

3rd Grade

4th Grade

5th Grade

6th Grade

7th grade math

8th grade math

9th grade math

10th grade math

11th grade math

12th grade math

Precalculus

Worksheets

Chapter wise Test

MCQ's

Math Dictionary

Graph Dictionary

Multiplicative tables

Math Teasers

NTSE

Chinese Numbers

CBSE Sample Papers