Inverse Problems on Compound Interest Time Period


 
 
Concept Explanation
 

Inverse Problems on Compound Interest - Finding Time Period

In this section, we shall discuss how to compute time period when Amount , Principal and rate is given.

Illustration: In what time Rs 800 amount to rs 882 at 5% per annum compounded annualy?

Solution: We have, P = Principal = Rs 800, A = amount = Rs 882 and Rate R = 5% per annum

A=Pleft ( 1+frac{R}{100} right )^{n}

882 =800 left ( 1+frac{5}{100} right )^{n}

frac{882}{800}=left ( 1+frac{1}{20} right )^{n}

frac{882}{800}=left ( frac{20+1}{20} right )^{n}

frac{882}{800}=left ( frac{21}{20} right )^{n}

frac{441}{400}=left ( frac{21}{20} right )^{2}

frac{21^{2}}{20^{2}}=left ( frac{21}{20} right )^{n}

left (frac{21}{20} right )^{2}=left ( frac{21}{20} right )^{n}

As the base is same. So, by comparing the powers, we have

n = 2

Hence, required time is 2 years.

Sample Questions
(More Questions for each concept available in Login)
Question : 1

In what time will Rs 4400 become Rs 4576 at 8% per annum interest compounded half-yearly?

Right Option : C
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Explanation
Question : 2

In what time will Rs 64000 amount to Rs 68921 at 5% per annum, interest being compounded half-yearly?

Right Option : A
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Explanation
Question : 3

Ishita invested a sum of Rs 12000 at 5% per annum compound interest. She received an amount of Rs 13230 after n years. Find the value of n.

Right Option : B
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Explanation
 
 
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