Simple Interest
MCQs Math


Question:     How much loan did Karen borrow 5 years ago at a rate of simple interest 3% per annum, if he paid $6842.5 to clear it?


Correct Answer  $5950

Solution And Explanation

Solution

Given,

Amount (A) = $6842.5

Rate of Simple Interest (R) = 3%

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

$6842.5 = P (1 + 3% × 5)

⇒ $6842.5 = P (1 + 3/100 × 5)

⇒ $6842.5 = P (1 + 3 × 5/100)

⇒ $6842.5 = P (1 + 15/100)

⇒ $6842.5 = P (100 + 15/100)

⇒ $6842.5 = P × 115/100

⇒ P × 115/100 = $6842.5

⇒ P = 6842.5/115/100

⇒ P = 6842.5 × 100/115

⇒ P = 6842.5 × 100/115

⇒ P = 684250/115

⇒ P = $5950

Thus, the sum borrowed (P) = $5950 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 = 3% per annum

Thus, Interest = 3% of principal

⇒ Interest = 3% of 100 = 3

Thus, Simple Interest for 1 year = 3

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 × 3 = 15

Thus, simple interest for 5 years = 15

Thus, Amount (A) = Principal + Interest

⇒ Amount = 100 + 15 = 115

Calculation of the Principal

Now,

∵ If the Amount is 115, then the Principal = 100

∴ If the Amount is 1, then the Principal = 100/115

∴ If the Amount is 6842.5, then the Principal = 100/115 × 6842.5

= 100 × 6842.5/115

= 684250/115

= 5950

Thus, Principal = $5950

Thus, the sum borrowed = $5950 Answer


Similar Questions

(1) What amount does Robert have to pay after 5 years if he takes a loan of $3100 at 9% simple interest?

(2) What amount does Jessica have to pay after 6 years if he takes a loan of $3750 at 5% simple interest?

(3) Sandra took a loan of $6900 at the rate of 9% simple interest per annum. If he paid an amount of $11868 to clear the loan, then find the time period of the loan.

(4) What amount does Charles have to pay after 5 years if he takes a loan of $3900 at 10% simple interest?

(5) How much loan did David borrow 5 years ago at a rate of simple interest 2% per annum, if he paid $5940 to clear it?

(6) Patricia took a loan of $4300 at the rate of 8% simple interest per annum. If he paid an amount of $7052 to clear the loan, then find the time period of the loan.

(7) Matthew took a loan of $6400 at the rate of 10% simple interest per annum. If he paid an amount of $10240 to clear the loan, then find the time period of the loan.

(8) James took a loan of $4000 at the rate of 10% simple interest per annum. If he paid an amount of $8000 to clear the loan, then find the time period of the loan.

(9) How much loan did Susan borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $6780 to clear it?

(10) William took a loan of $5000 at the rate of 7% simple interest per annum. If he paid an amount of $7100 to clear the loan, then find the time period of the loan.


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