Simple Interest
Math MCQs

Question :    What amount does Christopher have to pay after 6 years if he takes a loan of $4000 at 9% simple interest?

Correct Answer  $6160

Solution & Explanation

Solution

Given,

Principal (P) = $4000

Rate of Simple Interest (SI) = 9%

Time (t) = 6 years

Thus, Amount (A) = ?

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

Thus, here 9% simple interest means, Rate of Simple Interest (SI) is 9% 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) = $4000 × 9% × 6

= $4000 ×⁹/₁₀₀ × 6

= ^{4000 × 9 × 6}/₁₀₀

= ^{36000 × 6}/₁₀₀

= ²¹⁶⁰⁰⁰/₁₀₀

= $2160

Thus, Simple Interest = $2160

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 = $4000 + $2160

= $6160

Thus, Amount to be paid = $6160 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 = $4000

Rate of Simple Interest (SI) or (R) = 9%

And, Time (t) = 6 years

Thus, Amount (A)

= $4000 + ($4000 × 9% × 6)

= $4000 + ($4000 ×⁹/₁₀₀ × 6)

= $4000 + (^{4000 × 9 × 6}/₁₀₀)

= $4000 + (^{36000 × 6}/₁₀₀)

= $4000 + (²¹⁶⁰⁰⁰/₁₀₀)

= $4000 + $2160 = $6160

Thus, Amount (A) to be paid = $6160 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 9%

This, means, $9 per $100 per year

∵ For $100, the simple interest for 1 year = $9

∴ For $1, the simple interest for 1 year = ⁹/₁₀₀

∴ For $4000, the simple interest in 1 year

= ⁹/₁₀₀ × 4000

= ^{9 × 4000}/₁₀₀

= ³⁶⁰⁰⁰/₁₀₀ = $360

Thus, simple interest for 1 year = $360

Therefore, simple interest for 6 years

= Simple interest for 1 year × 6

= $360 × 6 = $2160

Thus, Simple Interest (SI) = $2160

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $4000 + $2160

= $6160

Thus, Amount to be paid = $6160 Answer

Similar Questions

(1) 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?

(2) In how much time a principal of $3100 will amount to $3472 at a simple interest of 4% per annum?

(3) Find the amount to be paid if Linda borrowed a sum of $5350 at 6% simple interest for 7 years.

(4) Calculate the amount due if Michael borrowed a sum of $3300 at 7% simple interest for 3 years.

(5) Daniel took a loan of $6200 at the rate of 10% simple interest per annum. If he paid an amount of $9920 to clear the loan, then find the time period of the loan.

(6) What amount does David have to pay after 5 years if he takes a loan of $3400 at 10% simple interest?

(7) Karen had to pay $4305.5 in order to furnish the loan taken 3 years before. If the rate of simple interest was 3% then find the sum borrowed.

(8) What amount does Jessica have to pay after 6 years if he takes a loan of $3750 at 10% simple interest?

(9) Karen took a loan of $5900 at the rate of 9% simple interest per annum. If he paid an amount of $9086 to clear the loan, then find the time period of the loan.

(10) Find the amount to be paid if Barbara borrowed a sum of $5550 at 9% simple interest for 8 years.