Simple Interest
Math MCQs

Question :    Calculate the amount due if Mary borrowed a sum of $3050 at 10% simple interest for 3 years.

Correct Answer  $3965

Solution & Explanation

Solution

Given,

Principal (P) = $3050

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) = $3050 × 10% × 3

= $3050 ×¹⁰/₁₀₀ × 3

= ^{3050 × 10 × 3}/₁₀₀

= ^{30500 × 3}/₁₀₀

= ⁹¹⁵⁰⁰/₁₀₀

= $915

Thus, Simple Interest = $915

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 = $3050 + $915

= $3965

Thus, Amount to be paid = $3965 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 = $3050

Rate of Simple Interest (SI) or (R) = 10%

And, Time (t) = 3 years

Thus, Amount (A)

= $3050 + ($3050 × 10% × 3)

= $3050 + ($3050 ×¹⁰/₁₀₀ × 3)

= $3050 + (^{3050 × 10 × 3}/₁₀₀)

= $3050 + (^{30500 × 3}/₁₀₀)

= $3050 + (⁹¹⁵⁰⁰/₁₀₀)

= $3050 + $915 = $3965

Thus, Amount (A) to be paid = $3965 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 $3050, the simple interest in 1 year

= ¹⁰/₁₀₀ × 3050

= ^{10 × 3050}/₁₀₀

= ³⁰⁵⁰⁰/₁₀₀ = $305

Thus, simple interest for 1 year = $305

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $305 × 3 = $915

Thus, Simple Interest (SI) = $915

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3050 + $915

= $3965

Thus, Amount to be paid = $3965 Answer

Similar Questions

(1) How much loan did Edward borrow 5 years ago at a rate of simple interest 5% per annum, if he paid $9500 to clear it?

(2) What amount does Thomas have to pay after 6 years if he takes a loan of $3800 at 6% simple interest?

(3) In how much time a principal of $3200 will amount to $3712 at a simple interest of 4% per annum?

(4) Find the amount to be paid if Elizabeth borrowed a sum of $5450 at 6% simple interest for 7 years.

(5) What amount does Joseph have to pay after 5 years if he takes a loan of $3700 at 5% simple interest?

(6) How much loan did Jessica borrow 5 years ago at a rate of simple interest 5% per annum, if he paid $7187.5 to clear it?

(7) William took a loan of $5000 at the rate of 10% simple interest per annum. If he paid an amount of $10000 to clear the loan, then find the time period of the loan.

(8) If William paid $3920 to settle his loan which he had taken 4 years before at a simple interest of 3%, then find the loan taken.

(9) Margaret took a loan of $6700 at the rate of 9% simple interest per annum. If he paid an amount of $10921 to clear the loan, then find the time period of the loan.

(10) William took a loan of $5000 at the rate of 9% simple interest per annum. If he paid an amount of $8150 to clear the loan, then find the time period of the loan.