Simple Interest
Math MCQs

Question :  ( 1 of 10 )  Calculate the amount due if Charles borrowed a sum of $3900 at 8% simple interest for 3 years.

Correct Answer  $4836

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 8%

Time (t) = 3 years

Thus, Amount (A) = ?

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

Thus, here 8% simple interest means, Rate of Simple Interest (SI) is 8% 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 × 8% × 3

= $3900 ×⁸/₁₀₀ × 3

= ^{3900 × 8 × 3}/₁₀₀

= ^{31200 × 3}/₁₀₀

= ⁹³⁶⁰⁰/₁₀₀

= $936

Thus, Simple Interest = $936

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 + $936

= $4836

Thus, Amount to be paid = $4836 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) = 8%

And, Time (t) = 3 years

Thus, Amount (A)

= $3900 + ($3900 × 8% × 3)

= $3900 + ($3900 ×⁸/₁₀₀ × 3)

= $3900 + (^{3900 × 8 × 3}/₁₀₀)

= $3900 + (^{31200 × 3}/₁₀₀)

= $3900 + (⁹³⁶⁰⁰/₁₀₀)

= $3900 + $936 = $4836

Thus, Amount (A) to be paid = $4836 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 8%

This, means, $8 per $100 per year

∵ For $100, the simple interest for 1 year = $8

∴ For $1, the simple interest for 1 year = ⁸/₁₀₀

∴ For $3900, the simple interest in 1 year

= ⁸/₁₀₀ × 3900

= ^{8 × 3900}/₁₀₀

= ³¹²⁰⁰/₁₀₀ = $312

Thus, simple interest for 1 year = $312

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $312 × 3 = $936

Thus, Simple Interest (SI) = $936

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $936

= $4836

Thus, Amount to be paid = $4836 Answer

Similar Questions

(1) Calculate the amount due if Barbara borrowed a sum of $3550 at 2% simple interest for 3 years.

(2) Calculate the amount due after 10 years if Barbara borrowed a sum of $5550 at a rate of 3% simple interest.

(3) Find the amount to be paid if Patricia borrowed a sum of $5150 at 9% simple interest for 7 years.

(4) Calculate the amount due if Joseph borrowed a sum of $3700 at 4% simple interest for 4 years.

(5) Calculate the amount due if Sarah borrowed a sum of $3850 at 3% simple interest for 3 years.

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

(7) What amount does Linda have to pay after 6 years if he takes a loan of $3350 at 7% simple interest?

(8) Margaret took a loan of $6700 at the rate of 7% simple interest per annum. If he paid an amount of $11390 to clear the loan, then find the time period of the loan.

(9) How much loan did Christopher borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $7200 to clear it?

(10) Jessica took a loan of $5500 at the rate of 8% simple interest per annum. If he paid an amount of $8580 to clear the loan, then find the time period of the loan.