Simple Interest
Math MCQs

Question :    Find the amount to be paid if Robert borrowed a sum of $5100 at 3% simple interest for 7 years.

Correct Answer  $6171

Solution & Explanation

Solution

Given,

Principal (P) = $5100

Rate of Simple Interest (SI) = 3%

Time (t) = 7 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) = $5100 × 3% × 7

= $5100 ׳/₁₀₀ × 7

= ^{5100 × 3 × 7}/₁₀₀

= ^{15300 × 7}/₁₀₀

= ¹⁰⁷¹⁰⁰/₁₀₀

= $1071

Thus, Simple Interest = $1071

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 = $5100 + $1071

= $6171

Thus, Amount to be paid = $6171 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 = $5100

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

And, Time (t) = 7 years

Thus, Amount (A)

= $5100 + ($5100 × 3% × 7)

= $5100 + ($5100 ׳/₁₀₀ × 7)

= $5100 + (^{5100 × 3 × 7}/₁₀₀)

= $5100 + (^{15300 × 7}/₁₀₀)

= $5100 + (¹⁰⁷¹⁰⁰/₁₀₀)

= $5100 + $1071 = $6171

Thus, Amount (A) to be paid = $6171 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 $5100, the simple interest in 1 year

= ³/₁₀₀ × 5100

= ^{3 × 5100}/₁₀₀

= ¹⁵³⁰⁰/₁₀₀ = $153

Thus, simple interest for 1 year = $153

Therefore, simple interest for 7 years

= Simple interest for 1 year × 7

= $153 × 7 = $1071

Thus, Simple Interest (SI) = $1071

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $5100 + $1071

= $6171

Thus, Amount to be paid = $6171 Answer

Similar Questions

(1) Calculate the amount due after 9 years if Jennifer borrowed a sum of $5250 at a rate of 5% simple interest.

(2) Mary had to pay $3507.5 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(3) How much loan did Brian borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $7920 to clear it?

(4) How much loan did Betty borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $7500 to clear it?

(5) What amount does Susan have to pay after 5 years if he takes a loan of $3650 at 6% simple interest?

(6) 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.

(7) Margaret took a loan of $6700 at the rate of 9% simple interest per annum. If he paid an amount of $11524 to clear the loan, then find the time period of the loan.

(8) Sarah took a loan of $5700 at the rate of 9% simple interest per annum. If he paid an amount of $9291 to clear the loan, then find the time period of the loan.

(9) Calculate the amount due after 10 years if Susan borrowed a sum of $5650 at a rate of 3% simple interest.

(10) Calculate the amount due after 9 years if Robert borrowed a sum of $5100 at a rate of 3% simple interest.