Simple Interest – Find the principal from two amounts: A sum amounts to Rs 850 in 3 years and Rs 925 in 4 years at simple interest. Find the principal (original sum).
Aptitude
Simple Interest
Difficulty: Easy
Choose an option
Answer
Correct Answer: Rs 625
Explanation
Introduction / Context:The per-year increase under SI equals the difference between consecutive-year amounts. Subtracting the appropriate multiple from an earlier amount reveals the principal.
Given Data / Assumptions:
- A3 = Rs 850
- A4 = Rs 925
Concept / Approach:Annual SI = A4 - A3. Then P = A3 - 3 * (annual SI).
Step-by-Step Solution:
Annual SI = 925 - 850 = Rs 75P = 850 - 3 * 75 = 850 - 225 = Rs 625Verification / Alternative check:
A4 check: 625 + 4 * 75 = 625 + 300 = 925Why Other Options Are Wrong:
- Rs 600 / 575 / 650: not consistent with both amounts.
- Data inadequate: data is sufficient in SI.
Common Pitfalls:
- Mistaking SI for compound interest.
Final Answer:Rs 625.