Aptitude - Simple Interest
11.
How much simple interest will Rs. 2000 earn in 18 months at 6% per annum ?
Answer
S.I. = Rs.
2000 x 18 x 612 x 100 
= Rs. 180
Answer :
Option BExplanation :
S.I. = Rs.
2000 x 18 x 612 x 100 = Rs. 180 12.
A sum of Rs. 10 is lent to be returned in 11 monthly instalments of Rs. 1 each, interest being simple. The rate of interest is :
Answer
Rs. 10 + S.I. on Rs. 10 for 11 months
= Rs. 11 + S.I. on Rs. 1 for (1 + 2 + 3 + ... + 10) months
⇒ Rs. 10 + S.I. on Rs. 1 for 110 months = Rs. 11 + S.I. on Rs. 1 for 55 months
⇒ S.I. on Rs. 1 for 55 months = Rs. 1
∴ Rate = 100 x 121 x 55 % = 21911%
Answer :
Option BExplanation :
Rs. 10 + S.I. on Rs. 10 for 11 months
= Rs. 11 + S.I. on Rs. 1 for (1 + 2 + 3 + ... + 10) months
⇒ Rs. 10 + S.I. on Rs. 1 for 110 months = Rs. 11 + S.I. on Rs. 1 for 55 months
⇒ S.I. on Rs. 1 for 55 months = Rs. 1
∴ Rate =
100 x 121 x 55 % = 21911% 13.
On a certain sum, the simple interest at the end of 12.5 years becomes 75% of the sum. What is the rate percent per annum ?
Answer
Let the sum be Rs. p. Then , S.I. = 75% of p = Rs. 3p4 and Time = 12.5 yrs
∴ Rate = 100 x 3p x 14 x p x 12.5 % p.a. = 6% p.a.
Answer :
Option CExplanation :
Let the sum be Rs. p. Then , S.I. = 75% of p = Rs. 3p4 and Time = 12.5 yrs
∴ Rate =
100 x 3p x 14 x p x 12.5 % p.a. = 6% p.a. 14.
The difference between the interests received from two different banks on Rs. 5000 for 2 years is Rs. 25. The difference between their rates is :
Answer
Let the rates be x% p.a. and y% p.a. Then,
5000 x x x 2100 − 5000 x y x 2100 = 25
⇒ 100(x − y) = 25 ⇒ x − y = 0.25
Required difference in rates = 0.25% p.a.
Answer :
Option DExplanation :
Let the rates be x% p.a. and y% p.a. Then,
5000 x x x 2100 − 5000 x y x 2100 = 25⇒ 100(x − y) = 25 ⇒ x − y = 0.25
Required difference in rates = 0.25% p.a.
15.
Kurti took a loan at simple interest at 6% in the first year with an increase of 0.5% in each subsequent year. She paid Rs. 3375 as interest after 4 years. How much loan did she take ?
Answer
Let the loan taken be Rs. p. Then,
p x 6100 x 1 + p x 6.5100 x 1 + p x 7100 x 1 + p x 7.5100 x 1 = 3375
⇒ (6 + 6.5 + 7 + 7.5) x p100 = 3375
⇒ p = 3375 x 10027 = 12500
Answer :
Option AExplanation :
Let the loan taken be Rs. p. Then,
p x 6100 x 1 + p x 6.5100 x 1 + p x 7100 x 1 + p x 7.5100 x 1 = 3375
⇒ (6 + 6.5 + 7 + 7.5) x p100 = 3375
⇒ p = 3375 x 10027 = 12500
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