Simple Interest
Math MCQs

Question :    Calculate the amount due after 9 years if Christopher borrowed a sum of $6000 at a rate of 8% simple interest.

Correct Answer  $10320

Solution & Explanation

Solution

Given,

Principal (P) = $6000

Rate of Simple Interest (SI) = 8%

Time (t) = 9 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) = $6000 × 8% × 9

= $6000 ×⁸/₁₀₀ × 9

= ^{6000 × 8 × 9}/₁₀₀

= ^{48000 × 9}/₁₀₀

= ⁴³²⁰⁰⁰/₁₀₀

= $4320

Thus, Simple Interest = $4320

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 = $6000 + $4320

= $10320

Thus, Amount to be paid = $10320 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 = $6000

Rate of Simple Interest (SI) or (R) = 8%

And, Time (t) = 9 years

Thus, Amount (A)

= $6000 + ($6000 × 8% × 9)

= $6000 + ($6000 ×⁸/₁₀₀ × 9)

= $6000 + (^{6000 × 8 × 9}/₁₀₀)

= $6000 + (^{48000 × 9}/₁₀₀)

= $6000 + (⁴³²⁰⁰⁰/₁₀₀)

= $6000 + $4320 = $10320

Thus, Amount (A) to be paid = $10320 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 $6000, the simple interest in 1 year

= ⁸/₁₀₀ × 6000

= ^{8 × 6000}/₁₀₀

= ⁴⁸⁰⁰⁰/₁₀₀ = $480

Thus, simple interest for 1 year = $480

Therefore, simple interest for 9 years

= Simple interest for 1 year × 9

= $480 × 9 = $4320

Thus, Simple Interest (SI) = $4320

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $6000 + $4320

= $10320

Thus, Amount to be paid = $10320 Answer

Similar Questions

(1) In how much time a principal of $3050 will amount to $3233 at a simple interest of 2% per annum?

(2) If Susan paid $4234 to settle his loan which he had taken 4 years before at a simple interest of 4%, then find the loan taken.

(3) Robert took a loan of $4200 at the rate of 7% simple interest per annum. If he paid an amount of $6258 to clear the loan, then find the time period of the loan.

(4) Calculate the amount due after 10 years if Charles borrowed a sum of $5900 at a rate of 2% simple interest.

(5) How much loan did Charles borrow 5 years ago at a rate of simple interest 5% per annum, if he paid $7375 to clear it?

(6) Donald took a loan of $7000 at the rate of 7% simple interest per annum. If he paid an amount of $11900 to clear the loan, then find the time period of the loan.

(7) If Thomas borrowed $3800 from a bank at a rate of 3% simple interest per annum then find the amount to be paid after 2 years.

(8) What amount does Jessica have to pay after 5 years if he takes a loan of $3750 at 7% simple interest?

(9) Mary took a loan of $4100 at the rate of 7% simple interest per annum. If he paid an amount of $6683 to clear the loan, then find the time period of the loan.

(10) What amount does Joseph have to pay after 6 years if he takes a loan of $3700 at 2% simple interest?