Single correct option
A sum of ₹8,000 lent at simple interest earns an interest of ₹2,160 in 3 years. If the rate of interest were 2 percentage points higher, how much interest would the same sum earn in 3 years?
- A. ₹2,480
- B. ₹2,592
- C. ₹2,700
- D. ₹2,640
Show answer and solution
Answer: (D) ₹2,640
SI = P × R × T/100 ⇒ 2160 = 8000 × R × 3/100 ⇒ R = 9% per annum.
At 11%: SI = 8000 × 11 × 3/100 = ₹2,640.
Shortcut: an extra 2% on ₹8,000 for 3 years adds 8000 × 0.02 × 3 = ₹480, so the new interest is 2160 + 480 = ₹2,640.
₹2,592 is what you get by increasing the interest by 20% (confusing percentage points with percent).
At 11%: SI = 8000 × 11 × 3/100 = ₹2,640.
Shortcut: an extra 2% on ₹8,000 for 3 years adds 8000 × 0.02 × 3 = ₹480, so the new interest is 2160 + 480 = ₹2,640.
₹2,592 is what you get by increasing the interest by 20% (confusing percentage points with percent).
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