An amount of 12000 was borrowed partly at 4% simple interest and partly at 6% compound interest. Find out the time period when interest obtained through simple interest equates to that of interest obtained through compound interest after 4 years. Assume that amount borrowed is in ratio 5 : 7
An amount of 12000 was borrowed partly at 4% simple interest and partly at 6% compound interest. Find out the time period when interest obtained through simple interest equates to that of interest obtained through compound interest after 4 years. Assume that amount borrowed is in ratio 5 : 7 Correct Answer 9.17
⇒ Amount borrowed is in ratio 5 : 7
hence,
principal amount for simple interest = 5 / 12 × 12000 = 5000
And amount borrowed at compound interest = 7000 (∵ 12000 – 5000 = 7000)
⇒ Simple interest = A = p (1 + rt) –––– (Rate: 4%)
⇒ Compound interest A = p (1 + (r / n)) nt (Rate: 6%) (here, t = 1)
Amount through compound interest = 7000 (1 + 0.06)4
⇒ 7000 (1.06)4 = 7000 × 1.262
⇒ Amount = 8, 834
Now,
⇒ interest earned = 8834 – 7000 = 1834
I = PRT / 100
Hence,
1834 = 5000 × 4 × t / 100
⇒ 1834 / 200 = t
⇒ t = 9.17 Years