Question:
How much loan did Thomas borrow 5 years ago at a rate of simple interest 4% per annum, if he paid $6960 to clear it?
Correct Answer
$5800
Solution And Explanation
Solution
Given,
Amount (A) = $6960
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
$6960 = P (1 + 4% × 5)
⇒ $6960 = P (1 + 4/100 × 5)
⇒ $6960 = P (1 + 4 × 5/100)
⇒ $6960 = P (1 + 20/100)
⇒ $6960 = P (100 + 20/100)
⇒ $6960 = P × 120/100
⇒ P × 120/100 = $6960
⇒ P = 6960/120/100
⇒ P = 6960 × 100/120
⇒ P = 6960 × 100/120
⇒ P = 696000/120
⇒ P = $5800
Thus, the sum borrowed (P) = $5800 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 6960, then the Principal = 100/120 × 6960
= 100 × 6960/120
= 696000/120
= 5800
Thus, Principal = $5800
Thus, the sum borrowed = $5800 Answer
Similar Questions
(1) Calculate the amount due if Christopher borrowed a sum of $4000 at 10% simple interest for 3 years.
(2) What amount does Charles have to pay after 5 years if he takes a loan of $3900 at 5% simple interest?
(3) Calculate the amount due if Jessica borrowed a sum of $3750 at 6% simple interest for 4 years.
(4) Find the amount to be paid if Sarah borrowed a sum of $5850 at 2% simple interest for 8 years.
(5) What amount will be due after 2 years if Anthony borrowed a sum of $3650 at a 9% simple interest?
(6) Calculate the amount due if Barbara borrowed a sum of $3550 at 9% simple interest for 4 years.
(7) If Kenneth paid $5400 to settle his loan which he had taken 4 years before at a simple interest of 2%, then find the loan taken.
(8) Calculate the amount due if David borrowed a sum of $3400 at 2% simple interest for 4 years.
(9) Find the amount to be paid if Linda borrowed a sum of $5350 at 9% simple interest for 7 years.
(10) Sarah took a loan of $5700 at the rate of 6% simple interest per annum. If he paid an amount of $8094 to clear the loan, then find the time period of the loan.