Compound Interest Part 3

Problem 1: P=?, R=14\tfrac{2}{3}%, T=2years, C.I-S.I=40,C.I=?

Solution: When such type of problems are given we have to follow one method as shown below.

Fraction for 14\tfrac{2}{7}% is \frac{1}{7}

7*7=49

14-15=1 is difference between C.I and S.I

1———>40

49———>?   \frac{40\times 49}{1}=1960 =Principle

15———>?  \frac{15\times 40}{1}=600 = C.I

14———>?\frac{40\times 14}{1}=560 = S.I

Problem 2: P=?, R=15%,T=2 years,C.I-S.I=180

Solution:

Fraction for 15% is \frac{3}{20}

20*20=400

129-120=9

9———>180

400——->?

\frac{180\times 400}{9}=8000 is principal

Compound Interest Part 2

Based on part 1 we will solve some problems in compound interest.

Problem 1: Find the principle and compound interest if the rate of interest is 10% and time is 2years and amount is 2420?

Solution:

R=10%

Time =2 years

Amount=2420

Principle=?

C.I=?

The fraction of 10% is \frac{1}{10}

10      11

10      11

10*10=100

11*11-121

Let 100 as a principle

121 as amount

121-100=21 is C.I

121———>2420

100———->?

\frac{2420\times 100}{121}=2000

121———->2420

21————–>?

\frac{2420\times 21}{121}=420

Principle =2000 and C.I=420

Problem 2: P=?, T=2 years,R_{1}=11\frac{1}{9}%, R_{2}=12\tfrac{1}{2}%,CI=480

Solution :

Convert 11\frac{1}{9}% into fraction i.e \frac{1}{9}

Convert 12\tfrac{1}{2}% into fraction i.e \frac{1}{8}

9      10

8       9

Cancel the common term 9 and the result is 8 and 10\frac{8}{10}=\frac{4}{5}

Here 4 is the principle and 5 is the amount

4-5=1 is C.I

1———->480

4———–> ?

\frac{480\times 4}{1}= 1920  is the principle.

Compound Interest Part 1

Problem 1: Find the successive discount of  37\tfrac{1}{2}% and 40%

Solution:

Fractional value of  37\tfrac{1}{2}% is \frac{3}{8}

Fractional value of 40% is  \frac{2}{5}

8        5

5         3

8*5=40

5*3=15

\frac{40}{15}=\frac{8}{3}

The result is 8 and 3

8 is the marked price and 3 is the S.P

8-3=5

\frac{5}{8}\times 100=62\frac{1}{2}%

There is a successive discount of  62\frac{1}{2}%

Problem 2: Find the successive increase of 11\frac{1}{9}% and 12\frac{1}{2}%

Solution:

Fraction for 11\frac{1}{9}% is\frac{1}{9}

Fraction for 12\frac{1}{2}% is \frac{1}{8}

9         10

8           9

Cancel common terms and the result is 8 and 10

\frac{8}{10}=\frac{4}{5}

4-5=1

\frac{1}{5}\times 100=25%

There is a successive increase of 25%

Note: when there is a successive decrease it is discount, When there is a successive increase it is compound interest.