Multiple choice

The difference between compound interest and simple interest on a certain sum at 30% rate of interest per annum in two years is Rs.1080. Find the sum. यदि एक निश्चित धनराशि पर 30% वार्षिक ब्याज की दर से दो वर्षों में चक्रवृद्धि ब्याज और साधारण ब्याज में अन्तर 1080 रू. है। धनराशि ज्ञात कीजिये।

  1. Rs. /रू.10800

  2. Rs. /रू.15000

  3. Rs. /रू.18000

  4. Rs. /रू.12000
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D Correct answer
Explanation

For 2 years at R = 30%: CI = P(1.3)² - P = 0.69P, SI = 2PR/100 = 0.6P. Difference = CI - SI = 0.69P - 0.6P = 0.09P. Given 0.09P = 1080, so P = 12000. Standard 2-year formula: CI - SI = PR²/10000. Here: P × 900/10000 = 1080, giving P = 12000. This difference is the 'interest on interest' for year 2.

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