Simple Interest
Math MCQs

Question :    Calculate the amount due if John borrowed a sum of $3200 at 7% simple interest for 3 years.

Correct Answer  $3872

Solution & Explanation

Solution

Given,

Principal (P) = $3200

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) = $3200 × 7% × 3

= $3200 ×⁷/₁₀₀ × 3

= ^{3200 × 7 × 3}/₁₀₀

= ^{22400 × 3}/₁₀₀

= ⁶⁷²⁰⁰/₁₀₀

= $672

Thus, Simple Interest = $672

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 = $3200 + $672

= $3872

Thus, Amount to be paid = $3872 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 = $3200

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

And, Time (t) = 3 years

Thus, Amount (A)

= $3200 + ($3200 × 7% × 3)

= $3200 + ($3200 ×⁷/₁₀₀ × 3)

= $3200 + (^{3200 × 7 × 3}/₁₀₀)

= $3200 + (^{22400 × 3}/₁₀₀)

= $3200 + (⁶⁷²⁰⁰/₁₀₀)

= $3200 + $672 = $3872

Thus, Amount (A) to be paid = $3872 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 $3200, the simple interest in 1 year

= ⁷/₁₀₀ × 3200

= ^{7 × 3200}/₁₀₀

= ²²⁴⁰⁰/₁₀₀ = $224

Thus, simple interest for 1 year = $224

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $224 × 3 = $672

Thus, Simple Interest (SI) = $672

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3200 + $672

= $3872

Thus, Amount to be paid = $3872 Answer

Similar Questions

(1) Calculate the amount due if Elizabeth borrowed a sum of $3450 at 5% simple interest for 3 years.

(2) Margaret took a loan of $6700 at the rate of 9% simple interest per annum. If he paid an amount of $10318 to clear the loan, then find the time period of the loan.

(3) Charles took a loan of $5800 at the rate of 8% simple interest per annum. If he paid an amount of $9976 to clear the loan, then find the time period of the loan.

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

(5) Patricia took a loan of $4300 at the rate of 10% simple interest per annum. If he paid an amount of $8600 to clear the loan, then find the time period of the loan.

(6) How much loan did John borrow 5 years ago at a rate of simple interest 5% per annum, if he paid $6500 to clear it?

(7) Lisa took a loan of $6100 at the rate of 7% simple interest per annum. If he paid an amount of $8662 to clear the loan, then find the time period of the loan.

(8) Calculate the amount due after 9 years if James borrowed a sum of $5000 at a rate of 8% simple interest.

(9) If James paid $3240 to settle his loan which he had taken 4 years before at a simple interest of 2%, then find the loan taken.

(10) In how much time a principal of $3100 will amount to $3472 at a simple interest of 4% per annum?