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) What amount does Linda have to pay after 5 years if he takes a loan of $3350 at 6% simple interest?

(2) Sarah took a loan of $5700 at the rate of 8% simple interest per annum. If he paid an amount of $9348 to clear the loan, then find the time period of the loan.

(3) John took a loan of $4400 at the rate of 6% simple interest per annum. If he paid an amount of $7040 to clear the loan, then find the time period of the loan.

(4) John took a loan of $4400 at the rate of 8% simple interest per annum. If he paid an amount of $6864 to clear the loan, then find the time period of the loan.

(5) Calculate the amount due after 10 years if Robert borrowed a sum of $5100 at a rate of 3% simple interest.

(6) Find the amount to be paid if Linda borrowed a sum of $5350 at 9% simple interest for 7 years.

(7) How much loan did John borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $5720 to clear it?

(8) In how much time a principal of $3100 will amount to $3596 at a simple interest of 4% per annum?

(9) Find the amount to be paid if James borrowed a sum of $5000 at 5% simple interest for 7 years.

(10) Thomas had to pay $4028 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.