Simple Interest
Math MCQs

Question :    What amount does Robert have to pay after 6 years if he takes a loan of $3100 at 8% simple interest?

Correct Answer  $4588

Solution & Explanation

Solution

Given,

Principal (P) = $3100

Rate of Simple Interest (SI) = 8%

Time (t) = 6 years

Thus, Amount (A) = ?

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

Thus, here 8% simple interest means, Rate of Simple Interest (SI) is 8% 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 × 8% × 6

= $3100 ×⁸/₁₀₀ × 6

= ^{3100 × 8 × 6}/₁₀₀

= ^{24800 × 6}/₁₀₀

= ¹⁴⁸⁸⁰⁰/₁₀₀

= $1488

Thus, Simple Interest = $1488

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 + $1488

= $4588

Thus, Amount to be paid = $4588 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) = 8%

And, Time (t) = 6 years

Thus, Amount (A)

= $3100 + ($3100 × 8% × 6)

= $3100 + ($3100 ×⁸/₁₀₀ × 6)

= $3100 + (^{3100 × 8 × 6}/₁₀₀)

= $3100 + (^{24800 × 6}/₁₀₀)

= $3100 + (¹⁴⁸⁸⁰⁰/₁₀₀)

= $3100 + $1488 = $4588

Thus, Amount (A) to be paid = $4588 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 8%

This, means, $8 per $100 per year

∵ For $100, the simple interest for 1 year = $8

∴ For $1, the simple interest for 1 year = ⁸/₁₀₀

∴ For $3100, the simple interest in 1 year

= ⁸/₁₀₀ × 3100

= ^{8 × 3100}/₁₀₀

= ²⁴⁸⁰⁰/₁₀₀ = $248

Thus, simple interest for 1 year = $248

Therefore, simple interest for 6 years

= Simple interest for 1 year × 6

= $248 × 6 = $1488

Thus, Simple Interest (SI) = $1488

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3100 + $1488

= $4588

Thus, Amount to be paid = $4588 Answer

Similar Questions

(1) Find the amount to be paid if David borrowed a sum of $5400 at 2% simple interest for 7 years.

(2) Calculate the amount due if James borrowed a sum of $3000 at 7% simple interest for 4 years.

(3) Calculate the amount due after 10 years if Charles borrowed a sum of $5900 at a rate of 4% simple interest.

(4) Calculate the amount due after 9 years if Barbara borrowed a sum of $5550 at a rate of 2% simple interest.

(5) Calculate the amount due if Mary borrowed a sum of $3050 at 5% simple interest for 4 years.

(6) In how much time a principal of $3200 will amount to $3456 at a simple interest of 4% per annum?

(7) What amount will be due after 2 years if Joshua borrowed a sum of $3950 at a 5% simple interest?

(8) Barbara took a loan of $5100 at the rate of 6% simple interest per annum. If he paid an amount of $7854 to clear the loan, then find the time period of the loan.

(9) Anthony had to pay $4558 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.

(10) Sandra took a loan of $6900 at the rate of 9% simple interest per annum. If he paid an amount of $12489 to clear the loan, then find the time period of the loan.