If the ratio of principal and amount after 1 year is 25 : 28, then the rate of interest per annum is:

English বাংলা
PREVIOUSLY ASKED IN:
PSC Miscellaneous Prelims 2018

Answer

12%

Explanation

Let the Principal (P) be Rs. 25 and the Amount (A) after 1 year be Rs. 28. We know that Simple Interest (I) = Amount - Principal = 28 - 25 = Rs. 3. Here, the Time period (T) is 1 year. We need to find the Rate of Interest (R). Using the formula: R = (I × 100) / (P × T) Substituting the values: R = (3 × 100) / (25 × 1) R = 300 / 25 = 12%. Therefore, the rate of interest per annum is 12%.

Key Points

  • > Ratio of Principal to Amount = 25 : 28.
  • > Interest for 1 year = Amount - Principal = 28 - 25 = 3 units.
  • > Formula for Rate: R = (SI × 100) / (P × T).
  • > Plugging in values: R = (3 × 100) / (25 × 1).
  • > 25 cancels 100 into 4. So, 3 × 4 = 12%.
  • > In ratio-based SI problems, you can assume the ratio values as absolute numbers for quick calculation.

Additional Information

Ratio Problems in Simple Interest

Principal (P)Amount (A)Interest (I)Rate % (I/P × 100)
10111(1/10) × 100 = 10%
20211(1/20) × 100 = 5%
25283(3/25) × 100 = 12%
50533(3/50) × 100 = 6%

Memory Tips

  • Scaling to 100: The base (Principal) is 25. To make the base 100 (which gives percentage directly), multiply by 4. So, multiply the interest (3) by 4. The result is directly 12%.
Mathematics Simple Interest Medium

Related Questions

04

একটি শ্রেণিতে মোট ছাত্রছাত্রীর মধ্যে \( \frac{5}{9} \) অংশ মেয়ে এবং বাকিরা ছেলে। যদি মেয়েদের \( \frac{1}{4} \) অংশ এবং ছেলেদের \( \frac{2}{3} \) অংশ অনুপস্থিত থাকে এবং উপস্থিত মোট ছাত্রছাত্রীর সংখ্যা 245 (সঠিক হিসাবের জন্য 244 ধরলে) হয়, তবে ওই শ্রেণিতে মোট কতজন ছাত্রছাত্রী আছে?

Medium