Question:
How much loan did Edward borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $9120 to clear it?
Correct Answer
$7600
Solution And Explanation
Solution
Given,
Amount (A) = $9120
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
$9120 = P (1 + 4% × 5)
⇒ $9120 = P (1 + 4/100 × 5)
⇒ $9120 = P (1 + 4 × 5/100)
⇒ $9120 = P (1 + 20/100)
⇒ $9120 = P (100 + 20/100)
⇒ $9120 = P × 120/100
⇒ P × 120/100 = $9120
⇒ P = 9120/120/100
⇒ P = 9120 × 100/120
⇒ P = 9120 × 100/120
⇒ P = 912000/120
⇒ P = $7600
Thus, the sum borrowed (P) = $7600 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 9120, then the Principal = 100/120 × 9120
= 100 × 9120/120
= 912000/120
= 7600
Thus, Principal = $7600
Thus, the sum borrowed = $7600 Answer
Similar Questions
(1) Donald took a loan of $7000 at the rate of 7% simple interest per annum. If he paid an amount of $9940 to clear the loan, then find the time period of the loan.
(2) Find the amount to be paid if Richard borrowed a sum of $5600 at 8% simple interest for 8 years.
(3) Calculate the amount due if Richard borrowed a sum of $3600 at 4% simple interest for 4 years.
(4) Find the amount to be paid if John borrowed a sum of $5200 at 4% simple interest for 8 years.
(5) If Andrew paid $5760 to settle his loan which he had taken 4 years before at a simple interest of 5%, then find the loan taken.
(6) In how much time a principal of $3200 will amount to $3840 at a simple interest of 5% per annum?
(7) Calculate the amount due after 10 years if Michael borrowed a sum of $5300 at a rate of 3% simple interest.
(8) What amount will be due after 2 years if John borrowed a sum of $3100 at a 5% simple interest?
(9) James took a loan of $4000 at the rate of 8% simple interest per annum. If he paid an amount of $5920 to clear the loan, then find the time period of the loan.
(10) Calculate the amount due after 10 years if Mary borrowed a sum of $5050 at a rate of 8% simple interest.