Simple Interest
Math MCQs

Question :    How much loan did Charles borrow 5 years ago at a rate of simple interest 5% per annum, if he paid $7375 to clear it?

Correct Answer  $5900

Solution & Explanation

Solution

Given,

Amount (A) = $7375

Rate of Simple Interest (R) = 5%

Time (T) = 5 years

Thus, Principal (P) = ?

Method (1) Using Formula

Calculation of the Principal using forumula when Amount, Time and Rate of Simple Interest are given

Formula to find the Principal (P)

Amount (A) = Principal (P) + Principal (P) × Rate (R) × Time (T)

⇒ Amount (A) = Principal (P) [1 + Rate (R) × Time (T)]

⇒ A = P (1 + RT)

Using the formula to find the Amount (A), the fourth can be calculated if any three of A, P, R, and T are given

In the given question, we need to find the Principal (P)

Therefore, by substituting, Amount, Rate, and Time, in the formula A = P (1 + RT) we get

$7375 = P (1 + 5% × 5)

⇒ $7375 = P (1 + ⁵/₁₀₀ × 5)

⇒ $7375 = P (1 + ^{5 × 5}/₁₀₀)

⇒ $7375 = P (1 + ²⁵/₁₀₀)

⇒ $7375 = P (^{100 + 25}/₁₀₀)

⇒ $7375 = P × ¹²⁵/₁₀₀

⇒ P × ¹²⁵/₁₀₀ = $7375

⇒ P = ⁷³⁷⁵/_¹²⁵/100

⇒ P = 7375 × ¹⁰⁰/₁₂₅

⇒ P = ^{7375 × 100}/₁₂₅

⇒ P = ⁷³⁷⁵⁰⁰/₁₂₅

⇒ P = $5900

Thus, the sum borrowed (P) = $5900 Answer

Method (1) Using Unitary Method

Calculation of the Principal using unitary method when Amount, Time and Rate of Simple Interest are given

Calculation of the Simple Interest

Let, the principal = 100

Here, since rate of simple interest = 5% per annum

Thus, Interest = 5% of principal

⇒ Interest = 5% of 100 = 5

Thus, Simple Interest for 1 year = 5

Calculation of the Amount

Since, in the question, time = 5 years

So, we need to calculate the simple interest for the given time period, which is 5 years

Thus, Simple Interest for 5 years = 5 × Simple Interest for 1 year

= 5 × 5 = 25

Thus, simple interest for 5 years = 25

Thus, Amount (A) = Principal + Interest

⇒ Amount = 100 + 25 = 125

Calculation of the Principal

Now,

∵ If the Amount is 125, then the Principal = 100

∴ If the Amount is 1, then the Principal = ¹⁰⁰/₁₂₅

∴ If the Amount is 7375, then the Principal = ¹⁰⁰/₁₂₅ × 7375

= ^{100 × 7375}/₁₂₅

= ⁷³⁷⁵⁰⁰/₁₂₅

= 5900

Thus, Principal = $5900

Thus, the sum borrowed = $5900 Answer

Similar Questions

(1) Calculate the amount due if Joseph borrowed a sum of $3700 at 9% simple interest for 3 years.

(2) Margaret had to pay $5002.5 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(3) Calculate the amount due after 10 years if Sarah borrowed a sum of $5850 at a rate of 2% simple interest.

(4) How much loan did Cynthia borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $8745 to clear it?

(5) Richard took a loan of $5200 at the rate of 8% simple interest per annum. If he paid an amount of $8944 to clear the loan, then find the time period of the loan.

(6) Calculate the amount due after 9 years if Michael borrowed a sum of $5300 at a rate of 9% simple interest.

(7) Matthew took a loan of $6400 at the rate of 8% simple interest per annum. If he paid an amount of $11008 to clear the loan, then find the time period of the loan.

(8) Jennifer took a loan of $4500 at the rate of 8% simple interest per annum. If he paid an amount of $7020 to clear the loan, then find the time period of the loan.

(9) In how much time a principal of $3000 will amount to $3240 at a simple interest of 2% per annum?

(10) Calculate the amount due after 9 years if Thomas borrowed a sum of $5800 at a rate of 3% simple interest.