Simple Interest Practice Test for Aptitude Exams -- Free Practice

Question 1

If a simple interest on a sum of money at 6% p.a. for 7 years is equal to twice of simple interest on another sum for 9 years at 5% p.a., the ratio (of the two sums) will be:

A

2 : 15✓✗

B

7 : 15✓✗

C

15 : 7✓✗

D

1 : 7✓✗

Explanation

Let the two sums be P₁ and P₂.
SI₁ = P₁ × 6 × 7100 = 42P₁100
SI₂ = P₂ × 5 × 9100 = 45P₂100
Given SI₁ = 2 × SI₂:
42P₁ = 90P₂
P₁ : P₂ = 90 : 42 = 15 : 7

Question 2

If the difference between the compound interest compounded annually and simple interest on a certain amount at 10% per annum for two years is Rs. 372, then the principal amount is:

A

Rs. 37,000✓✗

B

Rs. 37,200✓✗

C

Rs. 37,500✓✗

D

None of these✓✗

Explanation

For 2 years, CI − SI = P × (R/100)²
372 = P × (10100)² = P × 10010000 = P100
P = 372 × 100 = 37,200

Question 3

A sum of money, lent out at simple interest, doubles itself in 8 years. Find in how many years will the sum become triple (three times) of itself at the same rate per cent.

A

16 years✓✗

B

15 years✓✗

C

20 years✓✗

D

None of these✓✗

Explanation

Let the principal be P. Since it doubles in 8 years, SI for 8 years = P.
P = P × R × 8100, so R = 12.5% p.a.
For the sum to triple, SI required = 2P.
Time = 2P × 100P × 12.5 = 20012.5 = 16 years

Question 4

The annual rate of simple interest is 12.5%. In how many years does the principal double?

A

11 years✓✗

B

9 years✓✗

C

8 years✓✗

D

7 years✓✗

Explanation

For the principal to double, SI over T years = P.
P = P × 12.5 × T100
T = 10012.5 = 8 years

Question 5

A certain sum of money borrowed at simple interest amounts to Rs. 2688 in three years and to Rs. 2784 in four years. The rate per annum is:

A

4%✓✗

B

6%✓✗

C

5%✓✗

D

7%✓✗

Explanation

The increase from year 3 to year 4 is one year's interest:
SI for 1 year = 2784 - 2688 = 96
SI for 3 years = 3 × 96 = 288
Principal = 2688 - 288 = 2400
Rate = SI × 100P × T = 96 × 1002400 × 1 = 4%

Question 6

An investor is saving to pay off an obligation of Rs. 15,250 which is due in seven years. If the investor is earning 7.5% simple interest rate per annum, how much must be deposited now to meet the obligation?

A

Rs. 8,000✓✗

B

Rs. 9,000✓✗

C

Rs. 10,000✓✗

D

Rs. 11,000✓✗

Explanation

Let the deposit be P. After 7 years at 7.5% simple interest:
P × (1 + 0.075 × 7) = 15,250
P × 1.525 = 15,250
P = 15,2501.525 = 10,000

Question 7

A man invests an amount of Rs. 15,860 in the names of his three sons A, B and C in such a way that they get the same interest after 2, 3 and 4 years respectively. If the rate of interest is 5%, then the ratio of amount invested in the name of A, B and C is:

A

6 : 4 : 3✓✗

B

3 : 4 : 6✓✗

C

30 : 12 : 5✓✗

D

None of these✓✗

Explanation

Same interest means P_A × 2 = P_B × 3 = P_C × 4 = k (since SI = P × R × T / 100, with R constant)
P_A = k/2, P_B = k/3, P_C = k/4
Ratio = 12 : 13 : 14 = (multiplying by 12) 6 : 4 : 3

Question 8

In what time will a sum of money double itself at 6.25% p.a. simple interest?

A

5 years✓✗

B

8 years✓✗

C

12 years✓✗

D

16 years✓✗

Explanation

For the sum to double, SI over T years = P.
T = 1006.25 = 16 years

Question 9

The sum required to earn a monthly interest of Rs. 1,200 at 18% p.a. simple interest is:

A

Rs. 50,000✓✗

B

Rs. 60,000✓✗

C

Rs. 80,000✓✗

D

None of these✓✗

Explanation

Annual interest required = 1,200 × 12 = 14,400
P = 14,400 × 10018 = 80,000

Question 10

Sachin deposited Rs. 1,00,000 in his bank for 2 years at simple interest of 6%. How much interest would he earn? What is the final value of the deposit?

A

Rs. 6,000, Rs. 1,06,000✓✗

B

Rs. 15,000, Rs. 1,15,000✓✗

C

Rs. 11,600, Rs. 1,11,600✓✗

D

Rs. 12,000, Rs. 1,12,000✓✗

Explanation

SI = 1,00,000 × 6 × 2100 = 12,000
Final value = 1,00,000 + 12,000 = 1,12,000

Question 11

The simple interest on a sum of money at 5% p.a. for 8 years is equal to twice the simple interest on another sum for 6 years at 4% p.a. The ratio of the two sums will be:

A

5 : 6✓✗

B

3 : 5✓✗

C

6 : 5✓✗

D

2 : 3✓✗

Explanation

Let the sums be P1 and P2. P1 × 5 × 8 / 100 = 2 × P2 × 4 × 6 / 100, so 40 P1 = 48 P2.
P1 : P2 = 48 : 40 = 6 : 5.

Question 12

The simple interest on a certain sum of money is 125 times of the principal. If the rate of interest and time (in years) are numerically equal, find the rate of interest.

A

2%✓✗

B

3%✓✗

C

4%✓✗

D

None of these✓✗

Explanation

SI = P25. Using SI = P × R × T100 with R = T:
P25 = P × R²100
R² = 10025 = 4
R = 2%

Question 13

A sum of Rs. 46,875 was lent out at simple interest and at the end of 1 year 8 months the total amount was Rs. 50,000. Find the rate of interest percent per annum.

A

5%✓✗

B

6%✓✗

C

4%✓✗

D

8%✓✗

Explanation

SI = 50,000 - 46,875 = 3,125
Time = 1 year 8 months = 53 years
Rate = (SI × 100)/(P × T) = (3125 × 100)/(46875 × 53) = 31250078125 = 4%

Question 14

The sum required to earn a monthly interest of Rs. 1,200 at 18% per annum simple interest is:

A

Rs. 50,000✓✗

B

Rs. 60,000✓✗

C

Rs. 80,000✓✗

D

Rs. 66,000✓✗

Explanation

Annual interest = 1200 × 12 = Rs. 14,400
Sum = (Interest × 100) / (Rate × Time) = (14400 × 100) / 18 = Rs. 80,000

Question 15

A roadside tea stall merchant borrows Rs. 9,000 at 2.76% Simple Interest per annum. The principal and the interest are to be paid in 10 monthly instalments. If each instalment is double the preceding one, find the value of the last instalment.

A

Rs. 1,024✓✗

B

Rs. 4,608✓✗

C

Rs. 9,207✓✗

D

Rs. 4,096✓✗

Explanation

The 10 instalments form a GP with first term a and common ratio 2, so their sum = a(2¹⁰ - 1) = 1023a, which equals the total amount owed.
The interest for 10 months = 9000 × 2.76% × 1012 = Rs. 207, so 1023a = 9207 and a = 9.
The last (10th) instalment = a × 2⁹ = 9 × 512 = Rs. 4,608.

Question 16

A man invests Rs. 12,000 at 10% p.a. and another sum of money at 20% p.a. for one year. The total investment earns simple interest at 14% p.a. The total investment is:

A

Rs. 8,000✓✗

B

Rs. 20,000✓✗

C

Rs. 14,000✓✗

D

Rs. 16,000✓✗

Explanation

Let the second sum = y. Total interest = 12000 × 0.10 + y × 0.20 = 1200 + 0.2y
This must equal 14% of the total investment: 0.14 × (12000 + y) = 1680 + 0.14y
1200 + 0.2y = 1680 + 0.14y
0.06y = 480, so y = 8,000
Total investment = 12,000 + 8,000 = Rs. 20,000

Question 17

The difference in simple interest of a sum of Rs. 1,500 invested for 3 years at two different rates is Rs. 18. The difference in their rates is:

A

0.4✓✗

B

0.6✓✗

C

0.8✓✗

D

0.10✓✗

Explanation

SI difference = (P × T × ΔR) / 100
18 = (1500 × 3 × ΔR) / 100
18 = 45 × ΔR
ΔR = 0.4

Question 18

SI = 0.125P at 10% p.a. Find the time.

A

1.25 years✓✗

B

25 years✓✗

C

0.25 years✓✗

D

None of these✓✗

Explanation

SI = (P × R × T) / 100
0.125P = (P × 10 × T) / 100 = 0.1PT
T = 0.125 / 0.1 = 1.25 years

Question 19

Rs. 8,829 is invested into three different sectors in such a way that their amounts at 4% p.a. simple interest after 5, 6 and 8 years respectively are equal. Find each part of the sum.

A

Rs. 3,069, Rs. 2,970, Rs. 2,790✓✗

B

Rs. 3,089, Rs. 2,970, Rs. 2,790✓✗

C

Rs. 3,609, Rs. 2,970, Rs. 2,790✓✗

D

Rs. 3,069, Rs. 2,960, Rs. 2,760✓✗

Explanation

The amounts are equal, so P₁(1 + 0.20) = P₂(1 + 0.24) = P₃(1 + 0.32) = A (since 4% × 5 = 20%, 4% × 6 = 24% and 4% × 8 = 32%).
P₁ = A/1.20, P₂ = A/1.24 and P₃ = A/1.32.
Given P₁ + P₂ + P₃ = 8829, solving gives A = 3682.8, so P₁ = Rs. 3,069, P₂ = Rs. 2,970 and P₃ = Rs. 2,790.

Question 20

A sum of Rs. 12,000 amounts to Rs. 15,000 in 4 years at the rate of simple interest. Find the rate of interest.

A

6.25 %✓✗

B

4.25 %✓✗

C

5.9 %✓✗

D

5 %✓✗

Explanation

S.I. = 15000 – 12000 = Rs. 3000. R = 100 × S.I.P × T = 100 × 300012000 × 4 = 6.25%.

Question 21

John took a loan of Rs. 1500 with simple interest for as many years as the rate of interest. If he paid Rs. 540 as interest at the end of loan period, what was the rate of interest?

A

2 %✓✗

B

3 %✓✗

C

4 %✓✗

D

6 %✓✗

Explanation

Since time (in years) equals the rate R, S.I. = P × R × R100 = 1500R²100 = 15R². Given S.I. = 540: 15R² = 540, so R² = 36, giving R = 6%.

Question 22

At what rate percent per annum will sum of money double in 20 years?

A

1.2 %✓✗

B

2 %✓✗

C

4 %✓✗

D

5 %✓✗

Explanation

If a sum becomes z times in T years at simple interest, R = 100(z - 1)T. Here z = 2, T = 20: R = 100(2 - 1)20 = 5% p.a.

Question 23

Suresh borrows Rs. 10,000 for 2 years at 4 % p.a. simple interest. He lends it to Ramesh at 6 % p.a. for 2 years. Find his gain in this transaction per year.

A

Rs. 150✓✗

B

Rs. 200✓✗

C

Rs. 400✓✗

D

Rs. 450✓✗

Explanation

S.I. paid by Suresh = 10000 × 4 × 2100 = Rs. 800. S.I. received from Ramesh = 10000 × 6 × 2100 = Rs. 1200. Gain over 2 years = 1200 – 800 = Rs. 400. Gain per year = 4002 = Rs. 200.

Question 24

A sum was put at simple interest at a certain rate for 2 years. Had it been put at 2 % higher rate, it would have fetched Rs. 400 more. Find the sum.

A

8000✓✗

B

9000✓✗

C

10000✓✗

D

12000✓✗

Explanation

Let the sum be P and the original rate be R. P(R + 2)(2)100 – P(R)(2)100 = 400. Simplifying: 4P100 = 400, so P = Rs. 10,000.

Question 25

The S.I. on a certain sum of money for 4 years at 15 % per annum is Rs. 180 more than S.I. on same sum for 5 years at 10 % per annum. Find the sum.

A

1000✓✗

B

1200✓✗

C

1800✓✗

D

2000✓✗

Explanation

Let the sum be P. P × 15 × 4100 – P × 10 × 5100 = 180, giving 6P10 – 5P10 = 180, so P = Rs. 1800.