Question:
Thomas had to pay $4142 in order to furnish the loan taken 3 years before. If the rate of simple interest was 3% then find the sum borrowed.
Correct Answer
$3800
Solution And Explanation
Solution
Given,
Amount (A) = $4142
Rate of Simple Interest (R) = 3%
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
$4142 = P (1 + 3% × 3)
⇒ $4142 = P (1 + 3/100 × 3)
⇒ $4142 = P (1 + 3 × 3/100)
⇒ $4142 = P (1 + 9/100)
⇒ $4142 = P (100 + 9/100)
⇒ $4142 = P × 109/100
⇒ P × 109/100 = $4142
⇒ P = 4142/109/100
⇒ P = 4142 × 100/109
⇒ P = 4142 × 100/109
⇒ P = 414200/109
⇒ P = $3800
Thus, the sum borrowed (P) = $3800 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 = 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 × 3 = 9
Thus, simple interest for 3 years = 9
Thus, Amount (A) = Principal + Interest
⇒ Amount = 100 + 9 = 109
Calculation of the Principal
Now,
∵ If the Amount is 109, then the Principal = 100
∴ If the Amount is 1, then the Principal = 100/109
∴ If the Amount is 4142, then the Principal = 100/109 × 4142
= 100 × 4142/109
= 414200/109
= 3800
Thus, Principal = $3800
Thus, the sum borrowed = $3800 Answer
Similar Questions
(1) Find the amount to be paid if Christopher borrowed a sum of $6000 at 3% simple interest for 7 years.
(2) Calculate the amount due if Richard borrowed a sum of $3600 at 9% simple interest for 4 years.
(3) Find the amount to be paid if Susan borrowed a sum of $5650 at 6% simple interest for 8 years.
(4) Find the amount to be paid if Michael borrowed a sum of $5300 at 6% simple interest for 8 years.
(5) Calculate the amount due after 9 years if Joseph borrowed a sum of $5700 at a rate of 4% simple interest.
(6) What amount does Linda have to pay after 6 years if he takes a loan of $3350 at 5% simple interest?
(7) In how much time a principal of $3150 will amount to $3433.5 at a simple interest of 3% per annum?
(8) Elizabeth took a loan of $4900 at the rate of 9% simple interest per annum. If he paid an amount of $7987 to clear the loan, then find the time period of the loan.
(9) Calculate the amount due if Karen borrowed a sum of $3950 at 9% simple interest for 3 years.
(10) What amount does Karen have to pay after 5 years if he takes a loan of $3950 at 4% simple interest?