Simple Interest
MCQs Math


Question:     How much loan did Joshua borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $8280 to clear it?


Correct Answer  $6900

Solution And Explanation

Solution

Given,

Amount (A) = $8280

Rate of Simple Interest (R) = 4%

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

$8280 = P (1 + 4% × 5)

⇒ $8280 = P (1 + 4/100 × 5)

⇒ $8280 = P (1 + 4 × 5/100)

⇒ $8280 = P (1 + 20/100)

⇒ $8280 = P (100 + 20/100)

⇒ $8280 = P × 120/100

⇒ P × 120/100 = $8280

⇒ P = 8280/120/100

⇒ P = 8280 × 100/120

⇒ P = 8280 × 100/120

⇒ P = 828000/120

⇒ P = $6900

Thus, the sum borrowed (P) = $6900 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 = 4% per annum

Thus, Interest = 4% of principal

⇒ Interest = 4% of 100 = 4

Thus, Simple Interest for 1 year = 4

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 × 4 = 20

Thus, simple interest for 5 years = 20

Thus, Amount (A) = Principal + Interest

⇒ Amount = 100 + 20 = 120

Calculation of the Principal

Now,

∵ If the Amount is 120, then the Principal = 100

∴ If the Amount is 1, then the Principal = 100/120

∴ If the Amount is 8280, then the Principal = 100/120 × 8280

= 100 × 8280/120

= 828000/120

= 6900

Thus, Principal = $6900

Thus, the sum borrowed = $6900 Answer


Similar Questions

(1) Michael took a loan of $4600 at the rate of 10% simple interest per annum. If he paid an amount of $8280 to clear the loan, then find the time period of the loan.

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

(3) What amount does Thomas have to pay after 6 years if he takes a loan of $3800 at 10% simple interest?

(4) Christopher took a loan of $6000 at the rate of 10% simple interest per annum. If he paid an amount of $10200 to clear the loan, then find the time period of the loan.

(5) How much loan did Barbara borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $6660 to clear it?

(6) What amount does Sarah have to pay after 6 years if he takes a loan of $3850 at 7% simple interest?

(7) Find the amount to be paid if Barbara borrowed a sum of $5550 at 9% simple interest for 8 years.

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

(9) Emily had to pay $5462.5 in order to furnish the loan taken 3 years before. If the rate of simple interest was 5% then find the sum borrowed.

(10) Calculate the amount due after 10 years if James borrowed a sum of $5000 at a rate of 3% simple interest.


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