3. Which earns more simple interest in 1 year: ₹2000 at 6% or ₹3000 at 4%?
ABoth are equal at ₹120
B₹2000 at 6% earns more
C₹3000 at 4% earns more
D₹3000 at 4% earns ₹150
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Answer: A) Both are equal at ₹120
₹2000 at 6%: (2000×6×1)/100 = ₹120. ₹3000 at 4%: (3000×4×1)/100 = ₹120. Both equal ₹120.
4. At 8% per annum simple interest, in how many years will a sum of money double itself?
A12.5 years
B8 years
C10 years
D16 years
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Answer: A) 12.5 years
To double, S.I. = P. Take P = 100, S.I. = 100, R = 8. T = (100×100)/(100×8) = 10000/800 = 12.5 years.
5. The simple interest on a certain sum for 3 years at 8% per annum is ₹180 more than the interest on the same sum for 2 years at 9% per annum. Find the sum.
A6000
B3300
C3000
D2700
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Answer: C) 3000
Let P be the sum. (P×8×3)/100 − (P×9×2)/100 = 180 → (24P − 18P)/100 = 180 → 6P/100 = 180 → P = 18000/6 = ₹3000.