Simple Interest
Math MCQs

Question :    Calculate the amount due if Barbara borrowed a sum of $3550 at 10% simple interest for 3 years.

Correct Answer  $4615

Solution & Explanation

Solution

Given,

Principal (P) = $3550

Rate of Simple Interest (SI) = 10%

Time (t) = 3 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) = $3550 × 10% × 3

= $3550 ×¹⁰/₁₀₀ × 3

= ^{3550 × 10 × 3}/₁₀₀

= ^{35500 × 3}/₁₀₀

= ¹⁰⁶⁵⁰⁰/₁₀₀

= $1065

Thus, Simple Interest = $1065

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 = $3550 + $1065

= $4615

Thus, Amount to be paid = $4615 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 = $3550

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

And, Time (t) = 3 years

Thus, Amount (A)

= $3550 + ($3550 × 10% × 3)

= $3550 + ($3550 ×¹⁰/₁₀₀ × 3)

= $3550 + (^{3550 × 10 × 3}/₁₀₀)

= $3550 + (^{35500 × 3}/₁₀₀)

= $3550 + (¹⁰⁶⁵⁰⁰/₁₀₀)

= $3550 + $1065 = $4615

Thus, Amount (A) to be paid = $4615 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 $3550, the simple interest in 1 year

= ¹⁰/₁₀₀ × 3550

= ^{10 × 3550}/₁₀₀

= ³⁵⁵⁰⁰/₁₀₀ = $355

Thus, simple interest for 1 year = $355

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $355 × 3 = $1065

Thus, Simple Interest (SI) = $1065

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3550 + $1065

= $4615

Thus, Amount to be paid = $4615 Answer

Similar Questions

(1) Mary took a loan of $4100 at the rate of 10% simple interest per annum. If he paid an amount of $6560 to clear the loan, then find the time period of the loan.

(2) What amount does Sarah have to pay after 5 years if he takes a loan of $3850 at 6% simple interest?

(3) How much loan did Carol borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $7755 to clear it?

(4) Calculate the amount due after 9 years if William borrowed a sum of $5500 at a rate of 7% simple interest.

(5) How much loan did Laura borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $9420 to clear it?

(6) Calculate the amount due after 10 years if Christopher borrowed a sum of $6000 at a rate of 7% simple interest.

(7) Calculate the amount due if John borrowed a sum of $3200 at 7% simple interest for 4 years.

(8) Richard took a loan of $5200 at the rate of 7% simple interest per annum. If he paid an amount of $7748 to clear the loan, then find the time period of the loan.

(9) Find the amount to be paid if Susan borrowed a sum of $5650 at 7% simple interest for 7 years.

(10) How much loan did Barbara borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $6660 to clear it?