Simple Interest
Math MCQs

Question :    How much loan did Margaret borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $6985 to clear it?

Correct Answer  $6350

Solution & Explanation

Solution

Given,

Amount (A) = $6985

Rate of Simple Interest (R) = 2%

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

$6985 = P (1 + 2% × 5)

⇒ $6985 = P (1 + ²/₁₀₀ × 5)

⇒ $6985 = P (1 + ^{2 × 5}/₁₀₀)

⇒ $6985 = P (1 + ¹⁰/₁₀₀)

⇒ $6985 = P (^{100 + 10}/₁₀₀)

⇒ $6985 = P × ¹¹⁰/₁₀₀

⇒ P × ¹¹⁰/₁₀₀ = $6985

⇒ P = ⁶⁹⁸⁵/_¹¹⁰/100

⇒ P = 6985 × ¹⁰⁰/₁₁₀

⇒ P = ^{6985 × 100}/₁₁₀

⇒ P = ⁶⁹⁸⁵⁰⁰/₁₁₀

⇒ P = $6350

Thus, the sum borrowed (P) = $6350 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 = 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 × 2 = 10

Thus, simple interest for 5 years = 10

Thus, Amount (A) = Principal + Interest

⇒ Amount = 100 + 10 = 110

Calculation of the Principal

Now,

∵ If the Amount is 110, then the Principal = 100

∴ If the Amount is 1, then the Principal = ¹⁰⁰/₁₁₀

∴ If the Amount is 6985, then the Principal = ¹⁰⁰/₁₁₀ × 6985

= ^{100 × 6985}/₁₁₀

= ⁶⁹⁸⁵⁰⁰/₁₁₀

= 6350

Thus, Principal = $6350

Thus, the sum borrowed = $6350 Answer

Similar Questions

(1) Calculate the amount due after 10 years if Robert borrowed a sum of $5100 at a rate of 8% simple interest.

(2) Find the amount to be paid if Elizabeth borrowed a sum of $5450 at 3% simple interest for 7 years.

(3) Calculate the amount due if Charles borrowed a sum of $3900 at 10% simple interest for 3 years.

(4) Calculate the amount due after 9 years if John borrowed a sum of $5200 at a rate of 4% simple interest.

(5) What amount will be due after 2 years if James borrowed a sum of $3000 at a 6% simple interest?

(6) James had to pay $3450 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(7) Daniel took a loan of $6200 at the rate of 8% simple interest per annum. If he paid an amount of $9176 to clear the loan, then find the time period of the loan.

(8) If Joseph paid $4440 to settle his loan which he had taken 4 years before at a simple interest of 5%, then find the loan taken.

(9) Calculate the amount due if Linda borrowed a sum of $3350 at 6% simple interest for 4 years.

(10) What amount does Patricia have to pay after 5 years if he takes a loan of $3150 at 8% simple interest?