Simple Interest
Math MCQs

Question :    Calculate the amount due if Charles borrowed a sum of $3900 at 9% simple interest for 4 years.

Correct Answer  $5304

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 9%

Time (t) = 4 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% × 4

= $3900 ×⁹/₁₀₀ × 4

= ^{3900 × 9 × 4}/₁₀₀

= ^{35100 × 4}/₁₀₀

= ¹⁴⁰⁴⁰⁰/₁₀₀

= $1404

Thus, Simple Interest = $1404

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 + $1404

= $5304

Thus, Amount to be paid = $5304 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) = 4 years

Thus, Amount (A)

= $3900 + ($3900 × 9% × 4)

= $3900 + ($3900 ×⁹/₁₀₀ × 4)

= $3900 + (^{3900 × 9 × 4}/₁₀₀)

= $3900 + (^{35100 × 4}/₁₀₀)

= $3900 + (¹⁴⁰⁴⁰⁰/₁₀₀)

= $3900 + $1404 = $5304

Thus, Amount (A) to be paid = $5304 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 4 years

= Simple interest for 1 year × 4

= $351 × 4 = $1404

Thus, Simple Interest (SI) = $1404

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $1404

= $5304

Thus, Amount to be paid = $5304 Answer

Similar Questions

(1) What amount does Christopher have to pay after 6 years if he takes a loan of $4000 at 2% simple interest?

(2) Calculate the amount due if Joseph borrowed a sum of $3700 at 5% simple interest for 3 years.

(3) Calculate the amount due after 10 years if Patricia borrowed a sum of $5150 at a rate of 3% simple interest.

(4) Calculate the amount due if Patricia borrowed a sum of $3150 at 8% simple interest for 4 years.

(5) Calculate the amount due after 10 years if Robert borrowed a sum of $5100 at a rate of 8% simple interest.

(6) Karen took a loan of $5900 at the rate of 7% simple interest per annum. If he paid an amount of $8791 to clear the loan, then find the time period of the loan.

(7) Calculate the amount due after 10 years if Linda borrowed a sum of $5350 at a rate of 8% simple interest.

(8) What amount does Richard have to pay after 5 years if he takes a loan of $3600 at 8% simple interest?

(9) William had to pay $4025 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(10) Calculate the amount due if Charles borrowed a sum of $3900 at 2% simple interest for 4 years.