Multiple choice

If the difference of CI and SI on a principal for 3 years at 20% rate interest per annum is Rs. 448. Find the principal. यदि किसी मूलधन पर 3 वर्ष का चक्रवृद्धि ब्याज तथा साधारण ब्याज का अन्तर 20% वार्षिक ब्याज दर पर 448 रूपये है। मूलधन की गणना कीजिये ।

  1. 3500 Rs/रुपये

  2. 3800 Rs/रुपये

  3. 3600 Rs/रुपये

  4. 4000 Rs/रुपये
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A Correct answer
Explanation

For 3 years at rate r%, CI - SI = P × r² × (300 + r) / 100³. Substituting r=20 and CI-SI=448: 448 = P × 400 × 320 / 1000000, so 448 = P × 0.128, giving P = 3500. Alternatively, use the direct formula CI - SI for 3 years = P × (r/100)² × (3 + r/100). This captures the compounding effect that creates the difference.

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