Simple Interest
Math MCQs

Question :    Calculate the amount due if Charles borrowed a sum of $3900 at 9% simple interest for 3 years.

Correct Answer  $4953

Solution & Explanation

Solution

Given,

Principal (P) = $3900

Rate of Simple Interest (SI) = 9%

Time (t) = 3 years

Thus, Amount (A) = ?

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

Thus, here 9% simple interest means, Rate of Simple Interest (SI) is 9% 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 × 9% × 3

= $3900 ×⁹/₁₀₀ × 3

= ^{3900 × 9 × 3}/₁₀₀

= ^{35100 × 3}/₁₀₀

= ¹⁰⁵³⁰⁰/₁₀₀

= $1053

Thus, Simple Interest = $1053

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 + $1053

= $4953

Thus, Amount to be paid = $4953 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) = 9%

And, Time (t) = 3 years

Thus, Amount (A)

= $3900 + ($3900 × 9% × 3)

= $3900 + ($3900 ×⁹/₁₀₀ × 3)

= $3900 + (^{3900 × 9 × 3}/₁₀₀)

= $3900 + (^{35100 × 3}/₁₀₀)

= $3900 + (¹⁰⁵³⁰⁰/₁₀₀)

= $3900 + $1053 = $4953

Thus, Amount (A) to be paid = $4953 Answer

Method (3) Unitary Method

Calculation of Amount using Unitary Method

Calculation of Interest using Unitary Method

Here, given Rate of Simple Interest = 9%

This, means, $9 per $100 per year

∵ For $100, the simple interest for 1 year = $9

∴ For $1, the simple interest for 1 year = ⁹/₁₀₀

∴ For $3900, the simple interest in 1 year

= ⁹/₁₀₀ × 3900

= ^{9 × 3900}/₁₀₀

= ³⁵¹⁰⁰/₁₀₀ = $351

Thus, simple interest for 1 year = $351

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $351 × 3 = $1053

Thus, Simple Interest (SI) = $1053

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3900 + $1053

= $4953

Thus, Amount to be paid = $4953 Answer

Similar Questions

(1) What amount will be due after 2 years if Daniel borrowed a sum of $3550 at a 6% simple interest?

(2) Find the amount to be paid if Christopher borrowed a sum of $6000 at 8% simple interest for 8 years.

(3) What amount does Robert have to pay after 5 years if he takes a loan of $3100 at 5% simple interest?

(4) How much loan did Daniel borrow 5 years ago at a rate of simple interest 3% per annum, if he paid $7015 to clear it?

(5) What amount does Susan have to pay after 5 years if he takes a loan of $3650 at 10% simple interest?

(6) Daniel had to pay $4346 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.

(7) What amount does Linda have to pay after 6 years if he takes a loan of $3350 at 4% simple interest?

(8) Find the amount to be paid if William borrowed a sum of $5500 at 5% simple interest for 7 years.

(9) Calculate the amount due if Michael borrowed a sum of $3300 at 3% simple interest for 4 years.

(10) What amount will be due after 2 years if Paul borrowed a sum of $3850 at a 10% simple interest?