Simple Interest
Math MCQs

Question :    Calculate the amount due if Charles borrowed a sum of $3900 at 6% simple interest for 3 years.

Correct Answer  $4602

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 6%

Time (t) = 3 years

Thus, Amount (A) = ?

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

Thus, here 6% simple interest means, Rate of Simple Interest (SI) is 6% 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) = $3900 × 6% × 3

= $3900 ×⁶/₁₀₀ × 3

= ^{3900 × 6 × 3}/₁₀₀

= ^{23400 × 3}/₁₀₀

= ⁷⁰²⁰⁰/₁₀₀

= $702

Thus, Simple Interest = $702

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 = $3900 + $702

= $4602

Thus, Amount to be paid = $4602 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 = $3900

Rate of Simple Interest (SI) or (R) = 6%

And, Time (t) = 3 years

Thus, Amount (A)

= $3900 + ($3900 × 6% × 3)

= $3900 + ($3900 ×⁶/₁₀₀ × 3)

= $3900 + (^{3900 × 6 × 3}/₁₀₀)

= $3900 + (^{23400 × 3}/₁₀₀)

= $3900 + (⁷⁰²⁰⁰/₁₀₀)

= $3900 + $702 = $4602

Thus, Amount (A) to be paid = $4602 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 6%

This, means, $6 per $100 per year

∵ For $100, the simple interest for 1 year = $6

∴ For $1, the simple interest for 1 year = ⁶/₁₀₀

∴ For $3900, the simple interest in 1 year

= ⁶/₁₀₀ × 3900

= ^{6 × 3900}/₁₀₀

= ²³⁴⁰⁰/₁₀₀ = $234

Thus, simple interest for 1 year = $234

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $234 × 3 = $702

Thus, Simple Interest (SI) = $702

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $702

= $4602

Thus, Amount to be paid = $4602 Answer

Similar Questions

(1) Calculate the amount due if William borrowed a sum of $3500 at 10% simple interest for 4 years.

(2) What amount does David have to pay after 6 years if he takes a loan of $3400 at 10% simple interest?

(3) Calculate the amount due if Charles borrowed a sum of $3900 at 6% simple interest for 3 years.

(4) Jennifer took a loan of $4500 at the rate of 9% simple interest per annum. If he paid an amount of $7740 to clear the loan, then find the time period of the loan.

(5) Steven had to pay $5290 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(6) Sandra took a loan of $6900 at the rate of 7% simple interest per annum. If he paid an amount of $9798 to clear the loan, then find the time period of the loan.

(7) Michael took a loan of $4600 at the rate of 6% simple interest per annum. If he paid an amount of $7084 to clear the loan, then find the time period of the loan.

(8) Find the amount to be paid if Mary borrowed a sum of $5050 at 6% simple interest for 7 years.

(9) Charles had to pay $4251 in order to furnish the loan taken 3 years before. If the rate of simple interest was 3% then find the sum borrowed.

(10) Calculate the amount due if John borrowed a sum of $3200 at 3% simple interest for 4 years.