Simple Interest
MCQs Math


Question:     Margaret had to pay $4611 in order to furnish the loan taken 3 years before. If the rate of simple interest was 2% then find the sum borrowed.


Correct Answer  $4350

Solution And Explanation

Solution

Given,

Amount (A) = $4611

Rate of Simple Interest (R) = 2%

Time (T) = 3 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

$4611 = P (1 + 2% × 3)

⇒ $4611 = P (1 + 2/100 × 3)

⇒ $4611 = P (1 + 2 × 3/100)

⇒ $4611 = P (1 + 6/100)

⇒ $4611 = P (100 + 6/100)

⇒ $4611 = P × 106/100

⇒ P × 106/100 = $4611

⇒ P = 4611/106/100

⇒ P = 4611 × 100/106

⇒ P = 4611 × 100/106

⇒ P = 461100/106

⇒ P = $4350

Thus, the sum borrowed (P) = $4350 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 = 3 years

So, we need to calculate the simple interest for the given time period, which is 3 years

Thus, Simple Interest for 3 years = 3 × Simple Interest for 1 year

= 3 × 2 = 6

Thus, simple interest for 3 years = 6

Thus, Amount (A) = Principal + Interest

⇒ Amount = 100 + 6 = 106

Calculation of the Principal

Now,

∵ If the Amount is 106, then the Principal = 100

∴ If the Amount is 1, then the Principal = 100/106

∴ If the Amount is 4611, then the Principal = 100/106 × 4611

= 100 × 4611/106

= 461100/106

= 4350

Thus, Principal = $4350

Thus, the sum borrowed = $4350 Answer


Similar Questions

(1) Find the amount to be paid if Robert borrowed a sum of $5100 at 6% simple interest for 8 years.

(2) James took a loan of $4000 at the rate of 8% simple interest per annum. If he paid an amount of $6240 to clear the loan, then find the time period of the loan.

(3) Find the amount to be paid if Jennifer borrowed a sum of $5250 at 8% simple interest for 7 years.

(4) Find the amount to be paid if Sarah borrowed a sum of $5850 at 9% simple interest for 7 years.

(5) Charles took a loan of $5800 at the rate of 10% simple interest per annum. If he paid an amount of $10440 to clear the loan, then find the time period of the loan.

(6) Find the amount to be paid if Mary borrowed a sum of $5050 at 2% simple interest for 7 years.

(7) Calculate the amount due if Jennifer borrowed a sum of $3250 at 5% simple interest for 4 years.

(8) Nancy took a loan of $6300 at the rate of 7% simple interest per annum. If he paid an amount of $9387 to clear the loan, then find the time period of the loan.

(9) Calculate the amount due after 9 years if Charles borrowed a sum of $5900 at a rate of 5% simple interest.

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


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