Multiple choice

A sum placed at simple interest doubles itself in 12 years. In what time it will become 8 times? साधारण ब्याज पर रखी गयी एक राशि 12 वर्षों में दो गुना हो जाती है। वह कितने समय में स्वयं का 8 गुना हो जाएगी?

  1. 36 years/वर्ष

  2. 48 years/वर्ष

  3. 84 years/वर्ष

  4. 96 years/वर्ष
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C Correct answer
Explanation

If sum doubles in 12 years, simple interest equals principal in 12 years. So rate = 100/12% per year. To become 8 times, interest needed = 7 times principal. At rate (100/12)% per year, time needed = (7 × 100) / (100/12) = 7 × 12 = 84 years. Formula: Time = (RequiredInterest × PrincipalTime) / Principal

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