Simple Interest
Math MCQs

Question :    What amount will be due after 2 years if Andrew borrowed a sum of $3900 at a 9% simple interest?

Correct Answer  $4602

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 9%

Time (t) = 2 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% × 2

= $3900 ×⁹/₁₀₀ × 2

= ^{3900 × 9 × 2}/₁₀₀

= ^{35100 × 2}/₁₀₀

= ⁷⁰²⁰⁰/₁₀₀

= $702

Thus, Simple Interest = $702

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 + $702

= $4602

Thus, Amount to be paid = $4602 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) = 2 years

Thus, Amount (A)

= $3900 + ($3900 × 9% × 2)

= $3900 + ($3900 ×⁹/₁₀₀ × 2)

= $3900 + (^{3900 × 9 × 2}/₁₀₀)

= $3900 + (^{35100 × 2}/₁₀₀)

= $3900 + (⁷⁰²⁰⁰/₁₀₀)

= $3900 + $702 = $4602

Thus, Amount (A) to be paid = $4602 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 2 years

= Simple interest for 1 year × 2

= $351 × 2 = $702

Thus, Simple Interest (SI) = $702

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $702

= $4602

Thus, Amount to be paid = $4602 Answer

Similar Questions

(1) If Donald paid $4860 to settle his loan which he had taken 4 years before at a simple interest of 2%, then find the loan taken.

(2) Calculate the amount due after 9 years if David borrowed a sum of $5400 at a rate of 10% simple interest.

(3) What amount does Thomas have to pay after 5 years if he takes a loan of $3800 at 5% simple interest?

(4) What amount does James have to pay after 6 years if he takes a loan of $3000 at 9% simple interest?

(5) Calculate the amount due if James borrowed a sum of $3000 at 10% simple interest for 4 years.

(6) Find the amount to be paid if Charles borrowed a sum of $5900 at 10% simple interest for 8 years.

(7) Calculate the amount due if James borrowed a sum of $3000 at 5% simple interest for 4 years.

(8) Christopher took a loan of $6000 at the rate of 9% simple interest per annum. If he paid an amount of $10860 to clear the loan, then find the time period of the loan.

(9) If Barbara borrowed $3550 from a bank at a rate of 3% simple interest per annum then find the amount to be paid after 2 years.

(10) In how much time a principal of $3200 will amount to $3488 at a simple interest of 3% per annum?