Simple Interest Quiz

At what rate of simple interest per annum will a sum of money get doubled in 10 years?

• 8.5%

• 10 %

• 15 %

• 20 %

Answer explanation

To double a sum in 10 years with simple interest, use the formula: A = P(1 + rt). Here, A = 2P, t = 10. Thus, 2 = 1 + 10r, leading to r = 0.1 or 10%. Therefore, the correct answer is 10%.

At simple interest, a certain sum of money amounts to Rs. 1,250 in 2 years and to Rs. 2,000 in 5 years. Find the rate of interest per annum (rounded off to two places of decimal)

• 27.27%

• 33.33%

• 16.67%

• 11.11%

Answer explanation

The difference in amounts over 3 years (Rs. 2,000 - Rs. 1,250 = Rs. 750) gives the interest for 3 years. Thus, annual interest = Rs. 750 / 3 = Rs. 250. The principal is Rs. 1,250 - Rs. 500 (2 years interest) = Rs. 750. Rate = (250/750) * 100 = 33.33%.

Bharat borrowed a sum of `10,000 at a certain rate of simple interest for 2 years. If he paid an interest of `2,000 at the end of the period, then find the rate of interest per annum.

• 15%

• 25%

• 20%

• 10%

Answer explanation

Bharat paid `2000 as interest for 2 years on `10000. Using the formula for simple interest, I = PRT, we have 2000 = 10000 * R * 2. Solving for R gives R = 0.1 or 10%. Thus, the rate of interest per annum is 10%.

At what rate of simple interest per annum will ` 7500 get ` 9250 in 7 years?

• 1 33%

• 1 43%

• 1 53%

• 1 63%

Answer explanation

To find the rate of simple interest, use the formula: SI = PRT. Here, SI = 9250 - 7500 = 1750, P = 7500, and T = 7. Rearranging gives R = SI / (PT) = 1750 / (7500 * 7) = 0.0333 or 33%. Thus, the correct answer is 33%.

A sum of `7,500 gives a simple interest of `1,800 in 4 years. What is the rate of interest per annum?

• 5%

• 6%

• 4%

• 3%

Answer explanation

To find the rate of interest, use the formula: Simple Interest = Principal × Rate × Time. Rearranging gives Rate = Simple Interest / (Principal × Time). Here, Rate = 1800 / (7500 × 4) = 0.06 or 6%. Thus, the correct answer is 6%.

At what rate of simple interest will a sum of money triple itself in 8 years?

• 30%

• 20%

• 25%

• 35%

Answer explanation

To triple the amount in 8 years, the total interest earned must equal the principal. Using the formula for simple interest, I = PRT, we set 2P = PRT. Thus, R = 2/8 = 0.25 or 25%. Therefore, the correct answer is 25%.

Anil Kumar took a loan of `24,000 with simple interest for as many years as the rate of interest. If he paid `19,440 as interest at the end of the loan period, what was the rate of interest?

• 8.5%

• 10%

• 8%

• 9%

Answer explanation

Let the rate of interest be r%. The time period is also r years. Using the formula for simple interest, I = P * r * t / 100, we have 19440 = 24000 * r * r / 100. Solving gives r = 9%. Thus, the rate of interest is 9%.

The rate at which a sum becomes 2 times of itself in 10 years at simple interest is:

• 25%

• 15%

• 20%

• 10%

Answer explanation

To double a sum at simple interest, the formula is: A = P(1 + rt). Here, A = 2P, t = 10 years. Thus, 2 = 1 + 10r, leading to r = 0.1 or 10%. Therefore, the correct answer is 10%.

A sum of money invested at X% simple interest per annum amounts to ` 2,368 in 6 years and to `3,008 in 11 years. Find the value of X.

• 5

• 8

• 7.5

• 6

Answer explanation

The difference in amounts over 5 years (from 6 to 11 years) is `640. Using the formula for simple interest, I = P * r * t, we find that the interest rate X is 8%.

A woman borrowed some money on simple interest. After 4 years she returned 6 5 of money to the lender. What was the rate of interest?

• 3% p.a.

• 2% p.a

• 5% p.a.

• 4% p.a

Answer explanation

The woman returned 6.5 times the principal after 4 years. Using the formula for simple interest, I = PRT, we find R = (6.5P - P)/(4P) = 5%. Thus, the rate of interest is 5% p.a.