A man lends Tk. 10000 in four parts. If he gets 8% on TK. 2000, 7.5% on TK. 4000 and 8.5% on TK. 1400, what percent must he get for the remainder, if the average interest is 8.13%?
বিকল্পসমূহ (নিজের উত্তর যাচাই করতে ক্লিক করুন):
সঠিক উত্তর
2 (9)
বিস্তারিত ব্যাখ্যা ও বিশ্লেষণ:
Given:
- Total money lent = Tk. 10,000
- Tk. 2,000 at 8%
- Tk. 4,000 at 7.5%
- Tk. 1,400 at 8.5%
- Average interest = 8.13%
Step 1: Remaining amount
Remaining = 10,000 - (2,000 + 4,000 + 1,400) = Tk. 2,600
Step 2: Interest from first three parts
- 2000 × 8% = 160
- 4000 × 7.5% = 300
- 1400 × 8.5% = 119
Total known interest = 160 + 300 + 119 = Tk. 579
Step 3: Total required interest (average 8.13%)
Total interest = 10000 × 8.13% = Tk. 813
So, interest needed from remaining = 813 - 579 = Tk. 234
Step 4: Find rate on remaining Tk. 2,600
(2600 × r) / 100 = 234
⇒ 26r = 234
⇒ r = 234 / 26 = 9%
∴ Required rate of interest = 9%
