Simple Interest
Math MCQs

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

Correct Answer  $3379

Solution & Explanation

Solution

Given,

Principal (P) = $3100

Rate of Simple Interest (SI) = 3%

Time (t) = 3 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% × 3

= $3100 ׳/₁₀₀ × 3

= ^{3100 × 3 × 3}/₁₀₀

= ^{9300 × 3}/₁₀₀

= ²⁷⁹⁰⁰/₁₀₀

= $279

Thus, Simple Interest = $279

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 + $279

= $3379

Thus, Amount to be paid = $3379 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) = 3 years

Thus, Amount (A)

= $3100 + ($3100 × 3% × 3)

= $3100 + ($3100 ׳/₁₀₀ × 3)

= $3100 + (^{3100 × 3 × 3}/₁₀₀)

= $3100 + (^{9300 × 3}/₁₀₀)

= $3100 + (²⁷⁹⁰⁰/₁₀₀)

= $3100 + $279 = $3379

Thus, Amount (A) to be paid = $3379 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 3 years

= Simple interest for 1 year × 3

= $93 × 3 = $279

Thus, Simple Interest (SI) = $279

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3100 + $279

= $3379

Thus, Amount to be paid = $3379 Answer

Similar Questions

(1) Kenneth had to pay $5750 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(2) David took a loan of $4800 at the rate of 10% simple interest per annum. If he paid an amount of $9120 to clear the loan, then find the time period of the loan.

(3) What amount does Jennifer have to pay after 6 years if he takes a loan of $3250 at 4% simple interest?

(4) Calculate the amount due after 9 years if Sarah borrowed a sum of $5850 at a rate of 5% simple interest.

(5) How much loan did Cynthia borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $8745 to clear it?

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

(7) Find the amount to be paid if Robert borrowed a sum of $5100 at 4% simple interest for 7 years.

(8) Sarah had to pay $4196.5 in order to furnish the loan taken 3 years before. If the rate of simple interest was 3% then find the sum borrowed.

(9) Anthony took a loan of $6600 at the rate of 6% simple interest per annum. If he paid an amount of $10164 to clear the loan, then find the time period of the loan.

(10) In how much time a principal of $3200 will amount to $3840 at a simple interest of 4% per annum?