Simple Interest
Math MCQs

Question :    Calculate the amount due if Charles borrowed a sum of $3900 at 9% simple interest for 3 years.

Correct Answer  $4953

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 9%

Time (t) = 3 years

Thus, Amount (A) = ?

The Rate of Interest is always calculated per annum, i.e. per year.

Thus, here 9% simple interest means, Rate of Simple Interest (SI) is 9% per annum.

Method (1) Using Formula

Calculation of Simple Interest

Formula to Calculate Simple Interest

Simple Interest (SI) = Principal × Rate × Time

Thus, Simple Interest (SI) = $3900 × 9% × 3

= $3900 ×⁹/₁₀₀ × 3

= ^{3900 × 9 × 3}/₁₀₀

= ^{35100 × 3}/₁₀₀

= ¹⁰⁵³⁰⁰/₁₀₀

= $1053

Thus, Simple Interest = $1053

Calculation of Amount

The total money paid to the lender by a borrower is called the Amount.

In other words, sum of priciple and interest is called the Amount.

Formula to Calculate the Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $1053

= $4953

Thus, Amount to be paid = $4953 Answer

Method (2)

Calculation of Amount when Principal, Rate of Simple Interest and Time are given

Calculation of Amount directly using Principal, SI, and Time

Formula to calculate the Amount

Amount (A) = Principal (P) + Principal(P) × Rate of Interest (SI) × Time (t)

⇒ A = P + PRT

Here in the question, P = $3900

Rate of Simple Interest (SI) or (R) = 9%

And, Time (t) = 3 years

Thus, Amount (A)

= $3900 + ($3900 × 9% × 3)

= $3900 + ($3900 ×⁹/₁₀₀ × 3)

= $3900 + (^{3900 × 9 × 3}/₁₀₀)

= $3900 + (^{35100 × 3}/₁₀₀)

= $3900 + (¹⁰⁵³⁰⁰/₁₀₀)

= $3900 + $1053 = $4953

Thus, Amount (A) to be paid = $4953 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 9%

This, means, $9 per $100 per year

∵ For $100, the simple interest for 1 year = $9

∴ For $1, the simple interest for 1 year = ⁹/₁₀₀

∴ For $3900, the simple interest in 1 year

= ⁹/₁₀₀ × 3900

= ^{9 × 3900}/₁₀₀

= ³⁵¹⁰⁰/₁₀₀ = $351

Thus, simple interest for 1 year = $351

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $351 × 3 = $1053

Thus, Simple Interest (SI) = $1053

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $1053

= $4953

Thus, Amount to be paid = $4953 Answer

Similar Questions

(1) Calculate the amount due after 10 years if Linda borrowed a sum of $5350 at a rate of 4% simple interest.

(2) Find the amount to be paid if John borrowed a sum of $5200 at 3% simple interest for 7 years.

(3) Joseph took a loan of $5400 at the rate of 9% simple interest per annum. If he paid an amount of $8316 to clear the loan, then find the time period of the loan.

(4) Jennifer took a loan of $4500 at the rate of 6% simple interest per annum. If he paid an amount of $6120 to clear the loan, then find the time period of the loan.

(5) Karen took a loan of $5900 at the rate of 8% simple interest per annum. If he paid an amount of $9676 to clear the loan, then find the time period of the loan.

(6) What amount does David have to pay after 6 years if he takes a loan of $3400 at 7% simple interest?

(7) What amount does Christopher have to pay after 5 years if he takes a loan of $4000 at 4% simple interest?

(8) Jennifer had to pay $3445 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.

(9) Find the amount to be paid if Jennifer borrowed a sum of $5250 at 9% simple interest for 7 years.

(10) Calculate the amount due after 9 years if Michael borrowed a sum of $5300 at a rate of 6% simple interest.