Simple Interest
Math MCQs

Question :    Calculate the amount due if Robert borrowed a sum of $3100 at 7% simple interest for 3 years.

Correct Answer  $3751

Solution & Explanation

Solution

Given,

Principal (P) = $3100

Rate of Simple Interest (SI) = 7%

Time (t) = 3 years

Thus, Amount (A) = ?

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

Thus, here 7% simple interest means, Rate of Simple Interest (SI) is 7% 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) = $3100 × 7% × 3

= $3100 ×⁷/₁₀₀ × 3

= ^{3100 × 7 × 3}/₁₀₀

= ^{21700 × 3}/₁₀₀

= ⁶⁵¹⁰⁰/₁₀₀

= $651

Thus, Simple Interest = $651

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 = $3100 + $651

= $3751

Thus, Amount to be paid = $3751 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 = $3100

Rate of Simple Interest (SI) or (R) = 7%

And, Time (t) = 3 years

Thus, Amount (A)

= $3100 + ($3100 × 7% × 3)

= $3100 + ($3100 ×⁷/₁₀₀ × 3)

= $3100 + (^{3100 × 7 × 3}/₁₀₀)

= $3100 + (^{21700 × 3}/₁₀₀)

= $3100 + (⁶⁵¹⁰⁰/₁₀₀)

= $3100 + $651 = $3751

Thus, Amount (A) to be paid = $3751 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 7%

This, means, $7 per $100 per year

∵ For $100, the simple interest for 1 year = $7

∴ For $1, the simple interest for 1 year = ⁷/₁₀₀

∴ For $3100, the simple interest in 1 year

= ⁷/₁₀₀ × 3100

= ^{7 × 3100}/₁₀₀

= ²¹⁷⁰⁰/₁₀₀ = $217

Thus, simple interest for 1 year = $217

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $217 × 3 = $651

Thus, Simple Interest (SI) = $651

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3100 + $651

= $3751

Thus, Amount to be paid = $3751 Answer

Similar Questions

(1) Find the amount to be paid if Michael borrowed a sum of $5300 at 3% simple interest for 8 years.

(2) Margaret took a loan of $6700 at the rate of 9% simple interest per annum. If he paid an amount of $12730 to clear the loan, then find the time period of the loan.

(3) Michael took a loan of $4600 at the rate of 10% simple interest per annum. If he paid an amount of $7360 to clear the loan, then find the time period of the loan.

(4) Elizabeth took a loan of $4900 at the rate of 6% simple interest per annum. If he paid an amount of $7252 to clear the loan, then find the time period of the loan.

(5) Patricia took a loan of $4300 at the rate of 6% simple interest per annum. If he paid an amount of $6880 to clear the loan, then find the time period of the loan.

(6) What amount will be due after 2 years if Christopher borrowed a sum of $3500 at a 9% simple interest?

(7) What amount does James have to pay after 5 years if he takes a loan of $3000 at 9% simple interest?

(8) Linda took a loan of $4700 at the rate of 9% simple interest per annum. If he paid an amount of $7238 to clear the loan, then find the time period of the loan.

(9) Calculate the amount due after 10 years if Linda borrowed a sum of $5350 at a rate of 7% simple interest.

(10) Calculate the amount due if Joseph borrowed a sum of $3700 at 4% simple interest for 4 years.