Simple Interest
Math MCQs

Question :    Calculate the amount due if Karen borrowed a sum of $3950 at 3% simple interest for 3 years.

Correct Answer  $4305.5

Solution & Explanation

Solution

Given,

Principal (P) = $3950

Rate of Simple Interest (SI) = 3%

Time (t) = 3 years

Thus, Amount (A) = ?

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

Thus, here 3% simple interest means, Rate of Simple Interest (SI) is 3% 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) = $3950 × 3% × 3

= $3950 ׳/₁₀₀ × 3

= ^{3950 × 3 × 3}/₁₀₀

= ^{11850 × 3}/₁₀₀

= ³⁵⁵⁵⁰/₁₀₀

= $355.5

Thus, Simple Interest = $355.5

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 = $3950 + $355.5

= $4305.5

Thus, Amount to be paid = $4305.5 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 = $3950

Rate of Simple Interest (SI) or (R) = 3%

And, Time (t) = 3 years

Thus, Amount (A)

= $3950 + ($3950 × 3% × 3)

= $3950 + ($3950 ׳/₁₀₀ × 3)

= $3950 + (^{3950 × 3 × 3}/₁₀₀)

= $3950 + (^{11850 × 3}/₁₀₀)

= $3950 + (³⁵⁵⁵⁰/₁₀₀)

= $3950 + $355.5 = $4305.5

Thus, Amount (A) to be paid = $4305.5 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 3%

This, means, $3 per $100 per year

∵ For $100, the simple interest for 1 year = $3

∴ For $1, the simple interest for 1 year = ³/₁₀₀

∴ For $3950, the simple interest in 1 year

= ³/₁₀₀ × 3950

= ^{3 × 3950}/₁₀₀

= ¹¹⁸⁵⁰/₁₀₀ = $118.5

Thus, simple interest for 1 year = $118.5

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $118.5 × 3 = $355.5

Thus, Simple Interest (SI) = $355.5

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3950 + $355.5

= $4305.5

Thus, Amount to be paid = $4305.5 Answer

Similar Questions

(1) What amount will be due after 2 years if Robert borrowed a sum of $3050 at a 9% simple interest?

(2) Find the amount to be paid if James borrowed a sum of $5000 at 6% simple interest for 8 years.

(3) Anthony took a loan of $6600 at the rate of 7% simple interest per annum. If he paid an amount of $9372 to clear the loan, then find the time period of the loan.

(4) Calculate the amount due if Christopher borrowed a sum of $4000 at 7% simple interest for 3 years.

(5) Michael took a loan of $4600 at the rate of 6% simple interest per annum. If he paid an amount of $7084 to clear the loan, then find the time period of the loan.

(6) Christopher took a loan of $6000 at the rate of 8% simple interest per annum. If he paid an amount of $9840 to clear the loan, then find the time period of the loan.

(7) Find the amount to be paid if Robert borrowed a sum of $5100 at 4% simple interest for 7 years.

(8) Sandra took a loan of $6900 at the rate of 9% simple interest per annum. If he paid an amount of $11868 to clear the loan, then find the time period of the loan.

(9) Thomas took a loan of $5600 at the rate of 10% simple interest per annum. If he paid an amount of $11200 to clear the loan, then find the time period of the loan.

(10) How much loan did Emily borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $7425 to clear it?