Simple Interest problems
- 1. Find the difference in amount and principal for ? 4000 at the rate of 5% annual interest in 4 yr.
Options- A. ? 865.50
- B. ? 865
- C. ? 400
- D. ? 800 Discuss
Correct Answer: ? 800
Explanation:
The required difference in amount and principal is SI = A - P
Here, P = ? 4000, R = 5% T = 4 yr
According to the formula.
SI = (P x R x T) /100
= (4000 x 5 x 4)/100
= ? 800
- 2. A sum becomes its double in 10 yr. Find the annual rate of simple interest.
Options- A. 1%
- B. 5%
- C. 10%
- D. 20% Discuss
Correct Answer: 10%
Explanation:
Here, n = 2, T = 10 yr
? R = 100 (n - 1)/T
= 100(2 - 1)/10
= 100/10
= 10%
- 3. How long will a sum of money invested at 5% per annum SI take to increase its value by 50%
Options- A. 10 yr
- B. 12 yr
- C. 15 yr
- D. 7 yr Discuss
Correct Answer: 10 yr
Explanation:
Let sum be P.
? 50% of P = P/2 = SI
Now, P/2 = (P x 5 x T) / 100 [ as time = 10 yr]
? P/2 = 5PT / 100
? 1/2 = T/20
? = T = 10 yr
- 4. A certain sum becomes 8 fold in 15 yr at simple interest. What will be the rate interest?
Options- A. 465/3%
- B. 462/3%
- C. 465/8%
- D. 4612/11% Discuss
Correct Answer: 462/3%
Explanation:
Let sum = p
Then, after 15 yr
Sum = 8p
? SI = 8p - P = 7P
Now, 7P = (P x R x 15)/100
? 7 = 15R/100 = 3R/20
? R = (20 x 7)/3 = 140/3
= 462/3%
- 5. At a simple interest, a sum amounts to ? 1012 in 2 1/ 2 and becomes ? 1067.20 in 4 yr. What is the rate of interest
Options- A. 2.5%
- B. 3%
- C. 4%
- D. 5% Discuss
Correct Answer: 4%
Explanation:
Given, T1 = 21/2 yr, T2 = 4 Yr
According to the question.
[P + (P x R x 4)/100] - [P + (P x R x 2.5)/100] = 1067.20 - 1012 = 55.2
? (1.5 x P x R)/100 = 55.2
? PR = (552 x 100) / 15 = 3680
For 4 yr.
SI = PRT/100 = (3680 x 4)/100 = ? 147.2
? Sum (P) = 1067.2 - 147.2 = ? 920
We have, PR = 3680
? R = 3680/P = 3680/920 = 4%
- 6. At simple interest, a sum becomes 3 times in 20 yr. Find the time, in which the sum will be double at the same rate of interest.
Options- A. 8 yr
- B. 10 yr
- C. 12 yr
- D. 14 yr Discuss
Correct Answer: 10 yr
Explanation:
Here, n = 3, m = 2, T1 = 20 yr
? T2 = [(m -1) / (n - 1)] x T1
= (2 - 1) / (3 - 1) x 20 = 10 yr
- 7. Simple interest for the sum of ? 1500 is ? 30 in 4 yr and ? 60 in 8 yr. Find the rate of simple interest.
Options- A. 2.5%
- B. 1.5%
- C. 0.5%
- D. 0.25% Discuss
Correct Answer: 0.5%
Explanation:
Given, SI2 = 60, SI1 = 30, T1 = 4 yr, T2 = 8 yr
According to the question,
[(1500 x R x 8)/100] - [(1500 x R x 4)/100] = 60 - 30
? (6000 x R)/100 = 30
? R = 30/60 = 1/2 = 0.5%
- 8. At what rate per annum will the simple interest on a certain sum of money be 1/5 of the amount in 10 yr?
Options- A. 5%
- B. 2%
- C. 1%
- D. 8% Discuss
Correct Answer: 2%
Explanation:
Let sum = P, then SI = P/5 time = 10 yr.
? Rate = (100 x P)/(P x 5 x 10) = 2%
- 9. Mr. Deepak invested an amount of ? 21250 for 6 yr. At what rate of simple interest, will he obtain the total amount of ? 26350 at the end of 6 yr?
Options- A. 6% pa
- B. 5% pa
- C. 8% pa
- D. 12% pa Discuss
Correct Answer:
Explanation:
SI = 26350 - 21250 = ? 5100
? Rate = (SI x 100) / (Principal x Time)
= (5100 x 100) / (21250 x 6)
= 4%
- 10. The simple interest on ? 4000 in 3 yr at the rate of R % per annum equals equals to the simple interest on ? 5000 at the rate of 12% per annum in 2 yr The value of R is
Options- A. 6%
- B. 8%
- C. 9%
- D. 10% Discuss
Correct Answer: 10%
Explanation:
Since, the two simple interest are equal.
Then, (4000 x 3 x R)/100 = (5000 x 12 x 2)/100
? R = 10%
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