Simple Interest
Math MCQs

Question :    Calculate the amount due if John borrowed a sum of $3200 at 5% simple interest for 3 years.

Correct Answer  $3680

Solution & Explanation

Solution

Given,

Principal (P) = $3200

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) = $3200 × 5% × 3

= $3200 ×⁵/₁₀₀ × 3

= ^{3200 × 5 × 3}/₁₀₀

= ^{16000 × 3}/₁₀₀

= ⁴⁸⁰⁰⁰/₁₀₀

= $480

Thus, Simple Interest = $480

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 + $480

= $3680

Thus, Amount to be paid = $3680 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) = 5%

And, Time (t) = 3 years

Thus, Amount (A)

= $3200 + ($3200 × 5% × 3)

= $3200 + ($3200 ×⁵/₁₀₀ × 3)

= $3200 + (^{3200 × 5 × 3}/₁₀₀)

= $3200 + (^{16000 × 3}/₁₀₀)

= $3200 + (⁴⁸⁰⁰⁰/₁₀₀)

= $3200 + $480 = $3680

Thus, Amount (A) to be paid = $3680 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 $3200, the simple interest in 1 year

= ⁵/₁₀₀ × 3200

= ^{5 × 3200}/₁₀₀

= ¹⁶⁰⁰⁰/₁₀₀ = $160

Thus, simple interest for 1 year = $160

Therefore, simple interest for 3 years

= Simple interest for 1 year × 3

= $160 × 3 = $480

Thus, Simple Interest (SI) = $480

Calculation of Amount

Amount = Principal + Interest

Thus, Amount = $3200 + $480

= $3680

Thus, Amount to be paid = $3680 Answer

Similar Questions

(1) What amount does Elizabeth have to pay after 6 years if he takes a loan of $3450 at 9% simple interest?

(2) Find the amount to be paid if Barbara borrowed a sum of $5550 at 5% simple interest for 7 years.

(3) Elizabeth took a loan of $4900 at the rate of 7% simple interest per annum. If he paid an amount of $7644 to clear the loan, then find the time period of the loan.

(4) Richard took a loan of $5200 at the rate of 6% simple interest per annum. If he paid an amount of $7072 to clear the loan, then find the time period of the loan.

(5) What amount does Patricia have to pay after 6 years if he takes a loan of $3150 at 2% simple interest?

(6) Calculate the amount due if Barbara borrowed a sum of $3550 at 3% simple interest for 3 years.

(7) Betty took a loan of $6500 at the rate of 10% simple interest per annum. If he paid an amount of $11050 to clear the loan, then find the time period of the loan.

(8) Find the amount to be paid if Barbara borrowed a sum of $5550 at 10% simple interest for 8 years.

(9) Michael took a loan of $4600 at the rate of 6% simple interest per annum. If he paid an amount of $7084 to clear the loan, then find the time period of the loan.

(10) Calculate the amount due if Christopher borrowed a sum of $4000 at 4% simple interest for 3 years.