Simple Interest
Math MCQs

Question :    What amount does Richard have to pay after 5 years if he takes a loan of $3600 at 9% simple interest?

Correct Answer  $5220

Solution & Explanation

Solution

Given,

Principal (P) = $3600

Rate of Simple Interest (SI) = 9%

Time (t) = 5 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) = $3600 × 9% × 5

= $3600 ×⁹/₁₀₀ × 5

= ^{3600 × 9 × 5}/₁₀₀

= ^{32400 × 5}/₁₀₀

= ¹⁶²⁰⁰⁰/₁₀₀

= $1620

Thus, Simple Interest = $1620

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 = $3600 + $1620

= $5220

Thus, Amount to be paid = $5220 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 = $3600

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

And, Time (t) = 5 years

Thus, Amount (A)

= $3600 + ($3600 × 9% × 5)

= $3600 + ($3600 ×⁹/₁₀₀ × 5)

= $3600 + (^{3600 × 9 × 5}/₁₀₀)

= $3600 + (^{32400 × 5}/₁₀₀)

= $3600 + (¹⁶²⁰⁰⁰/₁₀₀)

= $3600 + $1620 = $5220

Thus, Amount (A) to be paid = $5220 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 $3600, the simple interest in 1 year

= ⁹/₁₀₀ × 3600

= ^{9 × 3600}/₁₀₀

= ³²⁴⁰⁰/₁₀₀ = $324

Thus, simple interest for 1 year = $324

Therefore, simple interest for 5 years

= Simple interest for 1 year × 5

= $324 × 5 = $1620

Thus, Simple Interest (SI) = $1620

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3600 + $1620

= $5220

Thus, Amount to be paid = $5220 Answer

Similar Questions

(1) Calculate the amount due if Susan borrowed a sum of $3650 at 6% simple interest for 4 years.

(2) How much loan did Edward borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $9120 to clear it?

(3) What amount does Jessica have to pay after 6 years if he takes a loan of $3750 at 4% simple interest?

(4) Sandra took a loan of $6900 at the rate of 6% simple interest per annum. If he paid an amount of $10626 to clear the loan, then find the time period of the loan.

(5) Calculate the amount due if Sarah borrowed a sum of $3850 at 8% simple interest for 3 years.

(6) Calculate the amount due if Christopher borrowed a sum of $4000 at 10% simple interest for 3 years.

(7) Calculate the amount due if Jennifer borrowed a sum of $3250 at 8% simple interest for 3 years.

(8) How much loan did Barbara borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $6105 to clear it?

(9) Matthew took a loan of $6400 at the rate of 6% simple interest per annum. If he paid an amount of $9472 to clear the loan, then find the time period of the loan.

(10) Calculate the amount due after 10 years if Michael borrowed a sum of $5300 at a rate of 2% simple interest.