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 Joseph borrowed a sum of $3700 at 9% simple interest for 4 years.

(2) What amount will be due after 2 years if John borrowed a sum of $3100 at a 6% simple interest?

(3) Calculate the amount due after 9 years if Sarah borrowed a sum of $5850 at a rate of 4% simple interest.

(4) Calculate the amount due after 9 years if Thomas borrowed a sum of $5800 at a rate of 7% simple interest.

(5) Calculate the amount due after 10 years if Karen borrowed a sum of $5950 at a rate of 9% simple interest.

(6) How much loan did David borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $6480 to clear it?

(7) Find the amount to be paid if Elizabeth borrowed a sum of $5450 at 4% simple interest for 8 years.

(8) Margaret had to pay $5002.5 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(9) Nancy had to pay $4648 in order to furnish the loan taken 3 years before. If the rate of simple interest was 4% then find the sum borrowed.

(10) How much loan did John borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $6240 to clear it?