A higher rate earns more — Aptitude Question
A higher rate earns more: A sum lent at a rate 3% higher would have earned ₹300 more in 4 years under simple… Answer and worked solution on CodeKairo.
- Topic: Simple & Compound Interest
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 75 seconds
Question
A sum lent at a rate 3% higher would have earned ₹300 more in 4 years under simple interest. What is the sum?
Options
- ₹2,000
- ₹2,500
- ₹3,000
- ₹3,500
Show the answer and the worked solution
Correct answer: B. ₹2,500
Worked solution
- Extra interest = P × 3 × 4 / 100 = 0.12P.
- 0.12P = 300 → P = ₹2,500.
Answer: ₹2,500.
The idea
The extra interest depends only on the extra rate, not on the original one — which is why the original rate is never given. P × Δr × T / 100 = extra.
Shortcut. 3% extra for 4 years is 12% of the sum, so 1% of the sum is 300 ÷ 12 = 25 and the sum is ₹2,500.
Common trap. ₹3,000 — it looks right because ₹300 is a neat 10% of it, but the extra rate over 4 years is 12%, which on ₹3,000 gives ₹360.
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