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) Mark took a loan of $6800 at the rate of 10% simple interest per annum. If he paid an amount of $12920 to clear the loan, then find the time period of the loan.

(2) Calculate the amount due after 9 years if Mary borrowed a sum of $5050 at a rate of 6% simple interest.

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

(4) Find the amount to be paid if Karen borrowed a sum of $5950 at 5% simple interest for 8 years.

(5) Find the amount to be paid if Karen borrowed a sum of $5950 at 2% simple interest for 7 years.

(6) Calculate the amount due if Susan borrowed a sum of $3650 at 6% simple interest for 4 years.

(7) Matthew took a loan of $6400 at the rate of 6% simple interest per annum. If he paid an amount of $10240 to clear the loan, then find the time period of the loan.

(8) If Paul paid $5264 to settle his loan which he had taken 4 years before at a simple interest of 3%, then find the loan taken.

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

(10) Calculate the amount due after 9 years if James borrowed a sum of $5000 at a rate of 3% simple interest.