Simple Interest
Math MCQs

Question :    What amount does Charles have to pay after 6 years if he takes a loan of $3900 at 10% simple interest?

Correct Answer  $6240

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 10%

Time (t) = 6 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) = $3900 × 10% × 6

= $3900 ×¹⁰/₁₀₀ × 6

= ^{3900 × 10 × 6}/₁₀₀

= ^{39000 × 6}/₁₀₀

= ²³⁴⁰⁰⁰/₁₀₀

= $2340

Thus, Simple Interest = $2340

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 + $2340

= $6240

Thus, Amount to be paid = $6240 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) = 10%

And, Time (t) = 6 years

Thus, Amount (A)

= $3900 + ($3900 × 10% × 6)

= $3900 + ($3900 ×¹⁰/₁₀₀ × 6)

= $3900 + (^{3900 × 10 × 6}/₁₀₀)

= $3900 + (^{39000 × 6}/₁₀₀)

= $3900 + (²³⁴⁰⁰⁰/₁₀₀)

= $3900 + $2340 = $6240

Thus, Amount (A) to be paid = $6240 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 $3900, the simple interest in 1 year

= ¹⁰/₁₀₀ × 3900

= ^{10 × 3900}/₁₀₀

= ³⁹⁰⁰⁰/₁₀₀ = $390

Thus, simple interest for 1 year = $390

Therefore, simple interest for 6 years

= Simple interest for 1 year × 6

= $390 × 6 = $2340

Thus, Simple Interest (SI) = $2340

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $2340

= $6240

Thus, Amount to be paid = $6240 Answer

Similar Questions

(1) Calculate the amount due if Christopher borrowed a sum of $4000 at 9% simple interest for 4 years.

(2) In how much time a principal of $3200 will amount to $3584 at a simple interest of 4% per annum?

(3) Linda took a loan of $4700 at the rate of 8% simple interest per annum. If he paid an amount of $8084 to clear the loan, then find the time period of the loan.

(4) Donald took a loan of $7000 at the rate of 6% simple interest per annum. If he paid an amount of $9940 to clear the loan, then find the time period of the loan.

(5) Karen took a loan of $5900 at the rate of 8% simple interest per annum. If he paid an amount of $10620 to clear the loan, then find the time period of the loan.

(6) Betty took a loan of $6500 at the rate of 8% simple interest per annum. If he paid an amount of $10140 to clear the loan, then find the time period of the loan.

(7) James took a loan of $4000 at the rate of 10% simple interest per annum. If he paid an amount of $7600 to clear the loan, then find the time period of the loan.

(8) Calculate the amount due if Barbara borrowed a sum of $3550 at 10% simple interest for 3 years.

(9) What amount does Patricia have to pay after 6 years if he takes a loan of $3150 at 10% simple interest?

(10) Calculate the amount due if Thomas borrowed a sum of $3800 at 10% simple interest for 3 years.