Simple Interest
Math MCQs

Question :    Calculate the amount due if Robert borrowed a sum of $3100 at 5% simple interest for 3 years.

Correct Answer  $3565

Solution & Explanation

Solution

Given,

Principal (P) = $3100

Rate of Simple Interest (SI) = 5%

Time (t) = 3 years

Thus, Amount (A) = ?

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

Thus, here 5% simple interest means, Rate of Simple Interest (SI) is 5% 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 × 5% × 3

= $3100 ×⁵/₁₀₀ × 3

= ^{3100 × 5 × 3}/₁₀₀

= ^{15500 × 3}/₁₀₀

= ⁴⁶⁵⁰⁰/₁₀₀

= $465

Thus, Simple Interest = $465

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 + $465

= $3565

Thus, Amount to be paid = $3565 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) = 5%

And, Time (t) = 3 years

Thus, Amount (A)

= $3100 + ($3100 × 5% × 3)

= $3100 + ($3100 ×⁵/₁₀₀ × 3)

= $3100 + (^{3100 × 5 × 3}/₁₀₀)

= $3100 + (^{15500 × 3}/₁₀₀)

= $3100 + (⁴⁶⁵⁰⁰/₁₀₀)

= $3100 + $465 = $3565

Thus, Amount (A) to be paid = $3565 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 5%

This, means, $5 per $100 per year

∵ For $100, the simple interest for 1 year = $5

∴ For $1, the simple interest for 1 year = ⁵/₁₀₀

∴ For $3100, the simple interest in 1 year

= ⁵/₁₀₀ × 3100

= ^{5 × 3100}/₁₀₀

= ¹⁵⁵⁰⁰/₁₀₀ = $155

Thus, simple interest for 1 year = $155

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $155 × 3 = $465

Thus, Simple Interest (SI) = $465

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3100 + $465

= $3565

Thus, Amount to be paid = $3565 Answer

Similar Questions

(1) What amount does Mary have to pay after 6 years if he takes a loan of $3050 at 6% simple interest?

(2) How much loan did Sharon borrow 5 years ago at a rate of simple interest 3% per annum, if he paid $8912.5 to clear it?

(3) If Nancy paid $4980 to settle his loan which he had taken 4 years before at a simple interest of 5%, then find the loan taken.

(4) What amount does Michael have to pay after 6 years if he takes a loan of $3300 at 3% simple interest?

(5) Calculate the amount due if Susan borrowed a sum of $3650 at 3% simple interest for 3 years.

(6) Find the amount to be paid if Michael borrowed a sum of $5300 at 10% simple interest for 7 years.

(7) Joseph took a loan of $5400 at the rate of 10% simple interest per annum. If he paid an amount of $10800 to clear the loan, then find the time period of the loan.

(8) Calculate the amount due if Mary borrowed a sum of $3050 at 6% simple interest for 4 years.

(9) Jessica took a loan of $5500 at the rate of 8% simple interest per annum. If he paid an amount of $9460 to clear the loan, then find the time period of the loan.

(10) Calculate the amount due if Patricia borrowed a sum of $3150 at 3% simple interest for 3 years.