Simple Interest
Math MCQs

Question :    Calculate the amount due if Charles borrowed a sum of $3900 at 10% simple interest for 4 years.

Correct Answer  $5460

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 10%

Time (t) = 4 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) = $3900 × 10% × 4

= $3900 ×¹⁰/₁₀₀ × 4

= ^{3900 × 10 × 4}/₁₀₀

= ^{39000 × 4}/₁₀₀

= ¹⁵⁶⁰⁰⁰/₁₀₀

= $1560

Thus, Simple Interest = $1560

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 = $3900 + $1560

= $5460

Thus, Amount to be paid = $5460 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 = $3900

Rate of Simple Interest (SI) or (R) = 10%

And, Time (t) = 4 years

Thus, Amount (A)

= $3900 + ($3900 × 10% × 4)

= $3900 + ($3900 ×¹⁰/₁₀₀ × 4)

= $3900 + (^{3900 × 10 × 4}/₁₀₀)

= $3900 + (^{39000 × 4}/₁₀₀)

= $3900 + (¹⁵⁶⁰⁰⁰/₁₀₀)

= $3900 + $1560 = $5460

Thus, Amount (A) to be paid = $5460 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 $3900, the simple interest in 1 year

= ¹⁰/₁₀₀ × 3900

= ^{10 × 3900}/₁₀₀

= ³⁹⁰⁰⁰/₁₀₀ = $390

Thus, simple interest for 1 year = $390

Therefore, simple interest for 4 years

= Simple interest for 1 year × 4

= $390 × 4 = $1560

Thus, Simple Interest (SI) = $1560

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $1560

= $5460

Thus, Amount to be paid = $5460 Answer

Similar Questions

(1) How much loan did Karen borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $6545 to clear it?

(2) Richard took a loan of $5200 at the rate of 8% simple interest per annum. If he paid an amount of $7696 to clear the loan, then find the time period of the loan.

(3) What amount will be due after 2 years if Kenneth borrowed a sum of $4000 at a 9% simple interest?

(4) Calculate the amount due if Barbara borrowed a sum of $3550 at 6% simple interest for 4 years.

(5) What amount will be due after 2 years if Joshua borrowed a sum of $3950 at a 6% simple interest?

(6) Calculate the amount due after 9 years if James borrowed a sum of $5000 at a rate of 7% simple interest.

(7) David took a loan of $4800 at the rate of 9% simple interest per annum. If he paid an amount of $7392 to clear the loan, then find the time period of the loan.

(8) How much loan did Paul borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $7370 to clear it?

(9) Calculate the amount due after 9 years if Karen borrowed a sum of $5950 at a rate of 10% simple interest.

(10) Nancy took a loan of $6300 at the rate of 6% simple interest per annum. If he paid an amount of $8946 to clear the loan, then find the time period of the loan.