Simple Interest
Math MCQs

Question :    Find the amount to be paid if Robert borrowed a sum of $5100 at 10% simple interest for 8 years.

Correct Answer  $9180

Solution & Explanation

Solution

Given,

Principal (P) = $5100

Rate of Simple Interest (SI) = 10%

Time (t) = 8 years

Thus, Amount (A) = ?

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

Thus, here 10% simple interest means, Rate of Simple Interest (SI) is 10% 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 × 10% × 8

= $5100 ×¹⁰/₁₀₀ × 8

= ^{5100 × 10 × 8}/₁₀₀

= ^{51000 × 8}/₁₀₀

= ⁴⁰⁸⁰⁰⁰/₁₀₀

= $4080

Thus, Simple Interest = $4080

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 + $4080

= $9180

Thus, Amount to be paid = $9180 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) = 10%

And, Time (t) = 8 years

Thus, Amount (A)

= $5100 + ($5100 × 10% × 8)

= $5100 + ($5100 ×¹⁰/₁₀₀ × 8)

= $5100 + (^{5100 × 10 × 8}/₁₀₀)

= $5100 + (^{51000 × 8}/₁₀₀)

= $5100 + (⁴⁰⁸⁰⁰⁰/₁₀₀)

= $5100 + $4080 = $9180

Thus, Amount (A) to be paid = $9180 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 10%

This, means, $10 per $100 per year

∵ For $100, the simple interest for 1 year = $10

∴ For $1, the simple interest for 1 year = ¹⁰/₁₀₀

∴ For $5100, the simple interest in 1 year

= ¹⁰/₁₀₀ × 5100

= ^{10 × 5100}/₁₀₀

= ⁵¹⁰⁰⁰/₁₀₀ = $510

Thus, simple interest for 1 year = $510

Therefore, simple interest for 8 years

= Simple interest for 1 year × 8

= $510 × 8 = $4080

Thus, Simple Interest (SI) = $4080

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $5100 + $4080

= $9180

Thus, Amount to be paid = $9180 Answer

Similar Questions

(1) Calculate the amount due if Susan borrowed a sum of $3650 at 2% simple interest for 3 years.

(2) Lisa took a loan of $6100 at the rate of 6% simple interest per annum. If he paid an amount of $9760 to clear the loan, then find the time period of the loan.

(3) What amount does Sarah have to pay after 5 years if he takes a loan of $3850 at 3% simple interest?

(4) Elizabeth took a loan of $4900 at the rate of 7% simple interest per annum. If he paid an amount of $8330 to clear the loan, then find the time period of the loan.

(5) Find the amount to be paid if John borrowed a sum of $5200 at 7% simple interest for 8 years.

(6) Richard took a loan of $5200 at the rate of 7% simple interest per annum. If he paid an amount of $8476 to clear the loan, then find the time period of the loan.

(7) What amount does Susan have to pay after 6 years if he takes a loan of $3650 at 4% simple interest?

(8) Find the amount to be paid if Patricia borrowed a sum of $5150 at 10% simple interest for 7 years.

(9) Find the amount to be paid if Joseph borrowed a sum of $5700 at 5% simple interest for 8 years.

(10) What amount does Jessica have to pay after 6 years if he takes a loan of $3750 at 3% simple interest?