Simple Interest
Math MCQs

Question :    Calculate the amount due if Christopher borrowed a sum of $4000 at 9% simple interest for 3 years.

Correct Answer  $5080

Solution & Explanation

Solution

Given,

Principal (P) = $4000

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) = $4000 × 9% × 3

= $4000 ×⁹/₁₀₀ × 3

= ^{4000 × 9 × 3}/₁₀₀

= ^{36000 × 3}/₁₀₀

= ¹⁰⁸⁰⁰⁰/₁₀₀

= $1080

Thus, Simple Interest = $1080

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 = $4000 + $1080

= $5080

Thus, Amount to be paid = $5080 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 = $4000

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

And, Time (t) = 3 years

Thus, Amount (A)

= $4000 + ($4000 × 9% × 3)

= $4000 + ($4000 ×⁹/₁₀₀ × 3)

= $4000 + (^{4000 × 9 × 3}/₁₀₀)

= $4000 + (^{36000 × 3}/₁₀₀)

= $4000 + (¹⁰⁸⁰⁰⁰/₁₀₀)

= $4000 + $1080 = $5080

Thus, Amount (A) to be paid = $5080 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 $4000, the simple interest in 1 year

= ⁹/₁₀₀ × 4000

= ^{9 × 4000}/₁₀₀

= ³⁶⁰⁰⁰/₁₀₀ = $360

Thus, simple interest for 1 year = $360

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $360 × 3 = $1080

Thus, Simple Interest (SI) = $1080

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $4000 + $1080

= $5080

Thus, Amount to be paid = $5080 Answer

Similar Questions

(1) How much loan did Jeffrey borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $9360 to clear it?

(2) Find the amount to be paid if Patricia borrowed a sum of $5150 at 5% simple interest for 8 years.

(3) Calculate the amount due if Charles borrowed a sum of $3900 at 8% simple interest for 3 years.

(4) If Margaret paid $4698 to settle his loan which he had taken 4 years before at a simple interest of 2%, then find the loan taken.

(5) Jennifer took a loan of $4500 at the rate of 8% simple interest per annum. If he paid an amount of $8100 to clear the loan, then find the time period of the loan.

(6) Thomas took a loan of $5600 at the rate of 9% simple interest per annum. If he paid an amount of $10640 to clear the loan, then find the time period of the loan.

(7) If Michael borrowed $3300 from a bank at a rate of 3% simple interest per annum then find the amount to be paid after 2 years.

(8) What amount does Joseph have to pay after 6 years if he takes a loan of $3700 at 3% simple interest?

(9) What amount will be due after 2 years if Andrew borrowed a sum of $3900 at a 4% simple interest?

(10) What amount does James have to pay after 5 years if he takes a loan of $3000 at 4% simple interest?