Simple Interest
Math MCQs

Question :    Calculate the amount due if Robert borrowed a sum of $3100 at 3% simple interest for 4 years.

Correct Answer  $3472

Solution & Explanation

Solution

Given,

Principal (P) = $3100

Rate of Simple Interest (SI) = 3%

Time (t) = 4 years

Thus, Amount (A) = ?

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

Thus, here 3% simple interest means, Rate of Simple Interest (SI) is 3% 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) = $3100 × 3% × 4

= $3100 ׳/₁₀₀ × 4

= ^{3100 × 3 × 4}/₁₀₀

= ^{9300 × 4}/₁₀₀

= ³⁷²⁰⁰/₁₀₀

= $372

Thus, Simple Interest = $372

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 = $3100 + $372

= $3472

Thus, Amount to be paid = $3472 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 = $3100

Rate of Simple Interest (SI) or (R) = 3%

And, Time (t) = 4 years

Thus, Amount (A)

= $3100 + ($3100 × 3% × 4)

= $3100 + ($3100 ׳/₁₀₀ × 4)

= $3100 + (^{3100 × 3 × 4}/₁₀₀)

= $3100 + (^{9300 × 4}/₁₀₀)

= $3100 + (³⁷²⁰⁰/₁₀₀)

= $3100 + $372 = $3472

Thus, Amount (A) to be paid = $3472 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 3%

This, means, $3 per $100 per year

∵ For $100, the simple interest for 1 year = $3

∴ For $1, the simple interest for 1 year = ³/₁₀₀

∴ For $3100, the simple interest in 1 year

= ³/₁₀₀ × 3100

= ^{3 × 3100}/₁₀₀

= ⁹³⁰⁰/₁₀₀ = $93

Thus, simple interest for 1 year = $93

Therefore, simple interest for 4 years

= Simple interest for 1 year × 4

= $93 × 4 = $372

Thus, Simple Interest (SI) = $372

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3100 + $372

= $3472

Thus, Amount to be paid = $3472 Answer

Similar Questions

(1) Calculate the amount due after 9 years if Charles borrowed a sum of $5900 at a rate of 2% simple interest.

(2) What amount does William have to pay after 6 years if he takes a loan of $3500 at 9% simple interest?

(3) Calculate the amount due after 9 years if Elizabeth borrowed a sum of $5450 at a rate of 4% simple interest.

(4) Thomas took a loan of $5600 at the rate of 6% simple interest per annum. If he paid an amount of $7952 to clear the loan, then find the time period of the loan.

(5) If Donna paid $5432 to settle his loan which he had taken 4 years before at a simple interest of 3%, then find the loan taken.

(6) Find the amount to be paid if Robert borrowed a sum of $5100 at 6% simple interest for 7 years.

(7) What amount does Charles have to pay after 5 years if he takes a loan of $3900 at 6% simple interest?

(8) Donald took a loan of $7000 at the rate of 7% simple interest per annum. If he paid an amount of $9940 to clear the loan, then find the time period of the loan.

(9) Calculate the amount due after 10 years if Jessica borrowed a sum of $5750 at a rate of 7% simple interest.

(10) What amount does David have to pay after 5 years if he takes a loan of $3400 at 8% simple interest?