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Answers
Answer:
Let :
• The sum of money be P
To Find :
• The rate of interest = ?
Solution :
• To calculate the rate of interest at first we have to set up equation by helping clue in the given Question
Calculation for 1st equation :
• CI= 40.80. T = 2 years.
R = r%
→ CI = P(1 + r/100)^t - P
⇒ 40.80 = P(1 + r/100)² - P
→ 40.80 = P(100 + r/100)² - P
→ 40.80 = P(100 + r)²/10000 - P
→ 40.80 = P(10000 + 200r + r2)/10000 - P
→ 40.80 = (10000P + 200Pr + Pr2)/10000 - P
40.80 = 10000P + 200Pr + Pr² - 10000P/ 10000
→ 40.80 = (200Pr + Pr²)/10000
→ 200Pr + Pr² = 408000
-(i)
99%
Calculation for 2nd equation :
• SI = 40. Time = 2years. R = r%
→ SI = P x T * R/100
40 P x 2 x r/100
→ 40 Pr/50
→
Pr = 2000-----(ii)
• Now putting the value of Pr in eq (i) :-]
→ 200Pr + Pr² = 408000
Pr(200 + r) = 408000
2000(200 + r) = 408000
→ 400000 + 2000r = 408000
→ 2000r = 408000-400000
→ 2000r = 8000
→ r = 4%.