Simple Interest and Compound Interest

1. A certain sum of money borrowed at a certain rate of interest in SIamounts to 6900/- in 3 years and 8100 in 7 years. Find the sum and rateof interest?

2. A certain sum of money borrowed at a certain rate of interest in SI, triplesitself in 8 years. In how many years will the same become 6 times itself atthe same rate of interest ?

3. Find the compound interest on a sum of 20,000/- at the rate of 20% perannum for 2 years interest being calculated for every 6 months?

4. The SI and CI on a particular sum of money for 2 years at a certain rate ofinterest is 1600/- and 1664/- respectively. Find the sum and ROI?

5. The difference between SI and CI on a particular sum of money at the rateof 5% per annum for 2 years is 40/-. Find the sum?

SI = ଵ Amount = Principal + interest

• The interest for any year will be calculated on the principal (Sumborrowed or lent)

• On a particular sum of money at a certain rate of interest. The SIfor any year will be same• Suppose if P=1000, ROI = 10% , Term = 3 years

SI CIInterest Amount Interest Amount100 1100 100 1100100 1200 110 1210100 1300 121 1331

1st

2nd

3rd

Basics :

• A = P(1 + ோଵ ) CI = Amount - Principal

n = number of times interest to be calculated• In CI, the interest for any year will be calculated on the amount to

be paid except the first year which is calculated in principal (Interestcalculated annually)

• On a particular sum of money at a certain rate of interest, the SIand CI for the 1st year will be same

• CI of (n+1)th year = CI of nth year + R% of CI of nth year• First year interest = R% of principal ( For both SI and CI, interest

calculated annually)

A certain sum of money borrowed at a certain rate of interest in SIamounts to 6900/- in 3 years and 8100 in 7 years. Find the sum and rateof interest?

Ans :A3 = P + 3I = 6900A7 = P + 7I = 8100 => I = 300 and P = 6000Principal = 6000Rate of Interest = ூ௧௦௧

Therefore Rate of interest = ଷ

1.

Sum = 6000 and Rate of interest = 5%

A certain sum of money borrowed at a certain rate of interest in SI,triples itself in 8 years. In how many years will the same become 6 timesitself at the same rate of interest ?

2.

Time Period = 20 years

Ans :Let P = 100 Amount = 300 and Interest = 200 for T = 8 years ( Amount triples itself ) For Amount = 600 Term = ? Interest = 500Therefore SI = ଵ => Interest Term

=> ூభூమ = భమ => ଶହ

௫ => x = 20 years

200 – 8500 – 20

Find the compound interest on a sum of 20,000/- at the rate of 20% perannum for 2 years interest being calculated for every 6 months?

3.

Ans :A = P(1 + ோ

ଵ ) CI = Amount - Principal A = 20000 (1 + ଵ

ଵ )ସFor 2 years n = 4 A = 29282/- CI = Amount - Principal

= 29282 – 20000= 9282/-

Compound Interest = 9282/-

20000( at 10%) = 20002000 + 200 = 22002200 + 220 = 24202420 + 242 = 2662total = 9282

The SI and CI on a particular sum of money for 2 years at a certain rateof interest is 1600/- and 1664/- respectively. Find the sum and ROI?

4.

Ans :

Sum = 10000 and ROI = 8%

1600 1664SI CI

1ST 800 8002ND 800 864

Rate of Interest = ூ௧௦௧

Rate of interest = ସ

= 8 % For 100rs - Interest 8/- For ? Rs – Interest 800/- Sum = 10000 ROI = 8%

100 – 810000 – 800

The difference between SI and CI on a particular sum of money at therate of 5% per annum for 2 years is 40/-. Find the sum?

5.

Ans :5 % of 1st year = 40100% of 1st year = ? (800)Similarly5% of P = 800100% of P = 16000Therefore Sum = 16000/-

Sum = 16000/-

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Problems for practice are given in the description of the video.

Practice problemson SI and CI

1. The si and ci on a particular sum of money at a certain rate of interest for 2years is 840/- and 861/- respectively. Find the rate of interest?

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