Discussion
In 3 years by compound interest, a sum becomes Rs. 900. But in 4 years by compound interest, the same sum becomes Rs. 1000. What is the sum and the rate of interest?
Answer: B
\[ A = P\left(1 + \frac{R}{100}\right)^{n}, \qquad \text{CI} = A - P, \qquad \text{SI} = \frac{PRn}{100} \]
The ratio of consecutive amounts gives the rate directly.
\[ 1 + \frac{R}{100} = \frac{1000}{900} = \frac{10}{9} = 1.1111 \quad\Longrightarrow\quad R = 11.11\% \]
Now work back three years from the Rs. 900:
\[ P = \frac{900}{(10/9)^{3}} = 900 \times \frac{729}{1000} = \text{Rs. } 656.10 \]
The rate \( \tfrac{1}{9} \) is what makes the cube \( \tfrac{729}{1000} \) exact, so the principal comes out to the paisa.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development