Simple Interest
Math MCQs

Question :    Calculate the amount due if Charles borrowed a sum of $3900 at 10% simple interest for 3 years.

Correct Answer  $5070

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 10%

Time (t) = 3 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% × 3

= $3900 ×¹⁰/₁₀₀ × 3

= ^{3900 × 10 × 3}/₁₀₀

= ^{39000 × 3}/₁₀₀

= ¹¹⁷⁰⁰⁰/₁₀₀

= $1170

Thus, Simple Interest = $1170

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 + $1170

= $5070

Thus, Amount to be paid = $5070 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) = 3 years

Thus, Amount (A)

= $3900 + ($3900 × 10% × 3)

= $3900 + ($3900 ×¹⁰/₁₀₀ × 3)

= $3900 + (^{3900 × 10 × 3}/₁₀₀)

= $3900 + (^{39000 × 3}/₁₀₀)

= $3900 + (¹¹⁷⁰⁰⁰/₁₀₀)

= $3900 + $1170 = $5070

Thus, Amount (A) to be paid = $5070 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 3 years

= Simple interest for 1 year × 3

= $390 × 3 = $1170

Thus, Simple Interest (SI) = $1170

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $1170

= $5070

Thus, Amount to be paid = $5070 Answer

Similar Questions

(1) Calculate the amount due after 10 years if Christopher borrowed a sum of $6000 at a rate of 8% simple interest.

(2) 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.

(3) Calculate the amount due after 10 years if John borrowed a sum of $5200 at a rate of 10% simple interest.

(4) How much loan did Daniel borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $7320 to clear it?

(5) Mark took a loan of $6800 at the rate of 10% simple interest per annum. If he paid an amount of $12240 to clear the loan, then find the time period of the loan.

(6) If Sarah borrowed $3850 from a bank at a rate of 3% simple interest per annum then find the amount to be paid after 2 years.

(7) If Lisa paid $4860 to settle his loan which he had taken 4 years before at a simple interest of 5%, then find the loan taken.

(8) Find the amount to be paid if Michael borrowed a sum of $5300 at 5% simple interest for 7 years.

(9) Calculate the amount due after 10 years if David borrowed a sum of $5400 at a rate of 9% simple interest.

(10) What amount does Elizabeth have to pay after 6 years if he takes a loan of $3450 at 4% simple interest?