Simple Interest
Math MCQs

Question :    If Andrew paid $5184 to settle his loan which he had taken 4 years before at a simple interest of 2%, then find the loan taken.

Correct Answer  $4800

Solution & Explanation

Solution

Given,

Amount (A) = $5184

Rate of Simple Interest (R) = 2%

Time (T) = 4 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

$5184 = P (1 + 2% × 4)

⇒ $5184 = P (1 + ²/₁₀₀ × 4)

⇒ $5184 = P (1 + ^{2 × 4}/₁₀₀)

⇒ $5184 = P (1 + ⁸/₁₀₀)

⇒ $5184 = P (^{100 + 8}/₁₀₀)

⇒ $5184 = P × ¹⁰⁸/₁₀₀

⇒ P × ¹⁰⁸/₁₀₀ = $5184

⇒ P = ⁵¹⁸⁴/_¹⁰⁸/100

⇒ P = 5184 × ¹⁰⁰/₁₀₈

⇒ P = ^{5184 × 100}/₁₀₈

⇒ P = ⁵¹⁸⁴⁰⁰/₁₀₈

⇒ P = $4800

Thus, the sum borrowed (P) = $4800 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 = 2% per annum

Thus, Interest = 2% of principal

⇒ Interest = 2% of 100 = 2

Thus, Simple Interest for 1 year = 2

Calculation of the Amount

Since, in the question, time = 4 years

So, we need to calculate the simple interest for the given time period, which is 4 years

Thus, Simple Interest for 4 years = 4 × Simple Interest for 1 year

= 4 × 2 = 8

Thus, simple interest for 4 years = 8

Thus, Amount (A) = Principal + Interest

⇒ Amount = 100 + 8 = 108

Calculation of the Principal

Now,

∵ If the Amount is 108, then the Principal = 100

∴ If the Amount is 1, then the Principal = ¹⁰⁰/₁₀₈

∴ If the Amount is 5184, then the Principal = ¹⁰⁰/₁₀₈ × 5184

= ^{100 × 5184}/₁₀₈

= ⁵¹⁸⁴⁰⁰/₁₀₈

= 4800

Thus, Principal = $4800

Thus, the sum borrowed = $4800 Answer

Similar Questions

(1) If Susan paid $4234 to settle his loan which he had taken 4 years before at a simple interest of 4%, then find the loan taken.

(2) Calculate the amount due if Jessica borrowed a sum of $3750 at 9% simple interest for 4 years.

(3) Charles had to pay $4134 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.

(4) Lisa took a loan of $6100 at the rate of 10% simple interest per annum. If he paid an amount of $9760 to clear the loan, then find the time period of the loan.

(5) Find the amount to be paid if Jennifer borrowed a sum of $5250 at 7% simple interest for 7 years.

(6) If Susan borrowed $3650 from a bank at a rate of 3% simple interest per annum then find the amount to be paid after 2 years.

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

(8) Calculate the amount due if Susan borrowed a sum of $3650 at 9% simple interest for 4 years.

(9) In how much time a principal of $3100 will amount to $3379 at a simple interest of 3% per annum?

(10) What amount does David have to pay after 6 years if he takes a loan of $3400 at 3% simple interest?