Aptitude : Simple Interest

(1) A sum of Rs. 900 amounts to Rs. 1080 in 2 years at simple interest. What is the rate of interest?

• (a)15 Percentage
• (b)7 Percentage
• (c)10 Percentage
• (d)12 Percentage

Answer

Correct Answer : (c) 10 Percentage
To find the rate of interest, we can use the formula for simple interest:
Simple Interest = (Principal × Rate × Time) / 100
We are given:
Principal (P) = Rs. 900
Amount (A) = Rs. 1080
Time (T) = 2 years
Let’s substitute these values into the formula and solve for the rate (R):
Simple Interest = A – P
Simple Interest = (P × R × T) / 100
A – P = (P × R × T) / 100
1080 – 900 = (900 × R × 2) / 100
180 = 1800R / 100
180 = 18R
R = 180 / 18
R = 10
Therefore, the rate of interest is 10%.

(2) If a sum of money at simple interest doubles in 5 years, what is the rate of interest?

• (a)10 Percentage
• (b)20 Percentage
• (c)30 Percentage
• (d)15 Percentage

Answer

Correct Answer : (b) 20 Percentage
To find the rate of interest, we can use the formula for simple interest:
Simple Interest = (Principal × Rate × Time) / 100
Let’s assume the principal amount is P, and we know that it doubles in 5 years. So the amount after 5 years will be 2P.
We are given:
Principal (P)
Time (T) = 5 years
Amount (A) = 2P
We need to find the Rate (R).
Using the formula for simple interest, we have:
Simple Interest = A – P
Simple Interest = (P × R × T) / 100
A – P = (P × R × T) / 100
2P – P = (P × R × 5) / 100
P = (P × R × 5) / 100
1 = (R × 5) / 100
100 = 5R
R = 100 / 5
R = 20
Therefore, the rate of interest is 20%.

(3) How long will it take for a sum of money to triple itself at 5% p.a. simple interest?

• (a)10 Years
• (b)15 Years
• (c)17 Years
• (d)20 Years

Answer

Correct Answer : (d) 20 Years
SI = PTR/100
Where:
SI is the simple interest
P is the principal amount
R is the interest rate
T is the time period in years
If the sum of money triples itself, then the simple interest is equal to the principal amount. So, SI = P.
We are also given that R = 5%.
We can now solve for T as follows:
T = (100SI) / (PR)
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T = (100 * P) / (P * 5%)
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T = 20 years

(4) A sum of money amounts to Rs. 6200 in 2 years and Rs. 6440 in 3 years. What is the rate of interest?

• (a)4 Percentage per Annum
• (b)5 Percentage per Annum
• (c)6 Percentage per Annum
• (d)7 Percentage per Annum

Answer

Correct Answer : (a) 4 Percentage per Annum
The simple interest earned in 1 year is Rs. (6440 – 6200) = Rs. 240.
The rate of interest is (100 * 240) / (6200 * 1) = 4% p.a.
The answer is 4% p.a.

(5) Ms. Walker invested a sum of Rs. 8000, part in Scheme X at 7% p.a. and the rest in Scheme Y at 10% p.a. If the total interest earned after 3 years is Rs. 2140, how much did she invest in Scheme Y?

• (a)3250 Rupees
• (b)3750 Rupees
• (c)4000 Rupees
• (d)3500 Rupees

Answer

Correct Answer : (d) 3500 Rupees
Let x be the amount invested in Scheme X.
The amount invested in Scheme Y is 8000 – x.
The interest earned in Scheme X is 0.07x * 3 = 0.21x.
The interest earned in Scheme Y is 0.10(8000 – x) = 800 – 0.1x.
The total interest earned is 0.21x + 800 – 0.1x = 2140.
Solving for x, we get x = 3500.
Therefore, Ms. Walker invested Rs. 3500 in Scheme Y.